







































Class . / . 5 

Book __ 































■ 







' 



■ 









■ 
























































































































. 






. 




I 















u 




f 




/ 


V 

Vjr 

A V 
> A 
A <J 


Professional Paper No. 54 


SoriM / A - Economic Geology. 76 
es \ B, Descriptive Geology, 95 






DEPARTMENT OF THE INTERIOR 

UNITED STATES GEOLOGICAL SURVEY 

CHARLES D. WALCOTT, DlRFXTOR 




GEOLOGY ANI) GOLD DEPOSITS 

OF THE 



AVALDEMAR LINDGREN 

AND 

FREDERICK LESLIE RANSOME 


I 


/ 





W A S HINGTON 

GOVERNMENT PRINTING OFFICE 

19 0 6 







A 4 












A 




Professional Paper No. 54 


c_- f A. Economic Geology, 76 
\ B, Descr.piTi 95 


DEPARTMENT OF THE INTERIOR 

UNITED STATES GEOLOGICAL SURVEY 

CHARLES D. WALCOTT. Dikectob 


GEOLOGY AND GOLD DEPOSITS 

OF THE 



AVAL DENIAL LIXDGREX 

AXD 1J 

FREDERICK LESLIE RAXSOME 



WASHINGTON 

GOVERNMENT PRINTING OFFICE 

19 06 

* j 

4 • s * 






•' V • 

'ivi . . } 












^OV IS 19ff7 

0. ulf D' 













I 


/ 


CONTENTS. 


Page. 

Synopsis of Part 1. 1 

Part I.—General Descriptions, Discussion, and Conclusions. 

Chapter I.—Introduction. 11 

Field work and acknowledgments. 11 

Literature. 15 

Chapter II.—General geology. 18 

Introductory statement. 18 

First geological survey of the district. 18 

Modification of earlier results. 19 

Basement rocks. 19 

Volcanic rocks. 20 

Form of the volcanic neck. 21 

Sedimentary deposits. 22 

Age of the eruptions. 23 

Geological structure of the district. 23 

Crystalline rocks of the prevolcanic plateau. 23 

Form of the volcanic neck. : . 24 

Breccia. 30 

Local bedding. 30 

Carbonaceous material. 31 

Intrusive masses within the volcanic neck. 32 

Outlying intrusive masses. 34 

Dikes of the volcanic period. 35 

Topographic development. 36 

Introduction. 36 

Prevolcanic conditions. 36 

Epoch of construction. 38 

Epoch of destruction. 39 

Chapter III.—Description and petrology of the metamorphic and igneous rocks, by L. C. Graton. 41 

Introduction. 41 

Plan and scope of the investigation. 41 

Outline of the rock formations. 42 

Ancient crystalline rocks. 43 

Granite. 43 

Pikes Peak granite. 43 

Cripple Creek granite. 45 

« Spring Creek granite. 47 

Relative age of the granites. 47 

Pegmatite. 48 

Gneiss. 48 

Womack gneiss. 48 

Other varieties. 50 


hi 











































TV 


CONTENTS. 


Chapter III.—Description and petrology of the metamorphic and igneous rocks—Continued. 
Ancient crystalline rocks—Continued. 

Schist. 

Olivine syenite.. 

Anorthosite.. 

Diabase . 

Tertiary volcanic rocks. 

Pbonolite. 

General description. 

Definition... 

Occurrence. 

Appearance. 

Mineralogical character... 

Feldspar. 

Nepheline. 

Sodalite and nosean.. 

Analcite. 

iEgirine and segirine-augite. 

Blue amphibole. 

Other minerals. 

Texture . 

Chemical character. 

Summary. 

Leucitophyre (?). 

Latite-phonolite. 

General description. 

Necessity for a new division. 

Definition. 

Occurrence... 

Appearance. 

Mineralogical character. 

General statement. 

Feldspar.. 

Pyroxene. 

Hornblende and biotite. 

Nosean, sodalite, and analcite. 

Apatite. 

Titanite.. 

Other minerals. 

Trachytic facies. 

Texture . 

Chemical character. 

Transitions to phonolite... 

Syenite. 

General description.. 

Mineralogical character. 

Chemical character... 

Trachydolerite (Bull Cliff type). 

General description. 

Mineralogical character. 

Chemical character. 

Summary. 

Basic dike rocks. 

General description. 


Page. 

51 

53 

55 

56 

56 

57 
57 
57 

57 

58 

59 
59 
61 
61 
62 
63 

63 

64 

65 

66 
67 

67 

68 
68 
68 
68 

70 

71 
71 

71 

72 

73 

73 

74 
74 

76 

77 

77 

78 

79 

83 

84 

84 

85 

87 

88 
88 
89* 
90 
90 
90 
90 


/ 






















































CONTENTS. 


V 


Chapter III.—Description and petrology of the metamorphic and igneous rocks—Continued. 
Tertiary volcanic rocks—Continued. 

Basic dike rocks—Continued. 

Trachydolerite (Isabella type). 

Vogesite. 

Monchiquite.*. 

Summary. 

Breccia. 

Rhyolite. 

Petrology of the district. 

Granite group. 

Olivine-syenite group. 

Rocks of the Cripple Creek volcano. 

Mineralogical characters. 

Chemical characters. 

Composition of the rocks expressed by diagrams. 

Average rock of the Cripple Creek volcano. 

Order of succession of the rocks. 

Summary. 

Chapter IV.—General mineralogy of the district. 

List of minerals. 

Notes on occurrence. 

Native elements. 

Gold. 

Silver. 

Copper.:. 

Tellurium. 

Tellurides. 

Coloradoite. 

Kalgoorlite.. 

Melonite. 

Altaite. 

Hessite. 

Petzite. 

Tetradymite. 

Nagyagite. 

Sylvanite. 

Krennerite... 

Calaverite. 

Oxidized tellurium compounds. 

Em monsite. 

Tellurite. 

Sulphides and sulphantimonites. 

Pvrite. 

Marcasite. 

Molybdenite. 

Stibnite. 

Cinnabar . 

Galena. 

Zinc blende (sphalerite). 

Chalcopyrite. 

Tetrahedrite. 

Chalcocite. 

Arsen opyrite. 


Page. 


91 

93 

95 

97 

97 

100 

101 

101 

102 

102 

103 

101 

107 

109 

113 

113 

114 
114 
114 
114 

114 

115 
115 
115 
115 

115 

116 
116 
116 
116 
116 
116 
116 
116 
116 

117 

118 
118 
12 » 
120 
120 
120 
120 
120 
121 
121 
121 
121 
121 
122 
122 





















































YI 


CONTENTS 


Page. 

Chapted IV.—General mineralogy of the district—Continued. 

Notes on occurrence—Continued. 

Oxides, carbonates, sulphates, silicates, etc. 122 

Fluorite. 122 

Quartz.•--- 123 

Chalcedony. 123 

Opal..'. 123 

Magnetite. 123 

Specularite.... 123 

Zircon. 123 

Rutile. 123 

Limonite...— 123 

Psilomelane and wad. 123 

Molybdite and ilsemannite. 123 

Calcite. 124 

Dolomite. 124 

Rhodochrosite.....c. 124 

Barite. 124 

Celestite. 124 

Alunite. 125 

Gypsum. 125 

Glockerite.-*. 125 

Basic hydrous strontium sulphate. 125 

Chalcanthite...... 126 

Mirabilite. 126 

Mallardite. 126 

Epsom ite. 126 

Other sulphates. 126 

Apatite. 126 

Wa veil ite. 126 

Hiibnerite. 127 

Titanite. 127 

Orthoclase. 127 

Microcline. 127 

Albite. 127 

Oligoclase, labradorite, and anorthite. 127 

Nepheline. 127 

Sodalite and nosean. 127 

Analcite. 127 

Stilbite and natrolite.*. 127 

Tourmaline. 127 

Olivine. 127 

Amphibole. 128 

Pyroxene. 128 

Muscovite. 128 

Biotite. 128 

Roscoelite. 128 

Chlorite. 128 

Serpentine. 128 

Kaolin. 128 

Cbrysocolla. 129 

Morencite(?), chloropal(?). 129 

Hydrocarbons. 129 

Coal. 129 






















































CONTENTS. 


Chapter V.—History and technology of the gold deposits 

History of mining development. 

Production. 

Mining.. 

Sampling. 

Processes of reduction. 

Technical details. 

Labor conditions. 

Financial conditions. 

Extent of productive territory. 

Chapter VI.—Preliminary review of the mining industry 

Earlier work in mining geology. 

Distribution of mines. 

Extent of underground development. 

Placers.. 

Chapter VII.—Structure of the gold deposits. 

Principal types of deposit. 

Lode fissures. j. 

Distribution. 

Direction of Assuring. 

Dips. 

Persistence. 

Influence of country rock. 

Structural features. 

Intersections. 

Origin of fissures... 

Chapter VIII.—The ores. 

General character... 

Composition and value... 

Fissure fillings.. 

Mineralogy.. 

Structure.. 

Exceptional varieties of veins.. 

Lead-zinc veins. 

Celestite vein. 

Biotite-feldspar vein. 

Chapter IX.—Processes of alteration. 

■Metasomatism in connection with vein formation- 

Extent of alteration. 

Character of alteration. 

Metasomatic minerals.. 

Metasomatic changes in phonolite. 

Metasomatic changes in syenite. 

Metasomatic changes in latite-phonolite. 

Metasomatic changes in breccia. 

Metasomatic changes in schist and gneiss. 

Metasomatic changes in basic dikes. 

Metasomatic changes in granite. 

Silicification and complete replacement. 

Sequence of processes. 

Evidence of aqueous action.. 

Oxidation. 

Original water level. 

Rock oxidation. 


VII 


Page. 

130 

130 

134 

135 
138 
138 
140 

142 

143 

146 

147 
147 
147 

151 

152 

. 153' 

153 
153 
153 

155 

156 
156 

159 

160 
165 
167 
169 

169 

170 
173 
173 
176 
182 
182 
183 

183 

184 
184 
184 

184 

185 
188 
188 
189 

191 

192 

192 

193 
195 

195 

196 

196 

197 
197 


























































VIII 


CONTENTS. 


Chapter IX.—Processes of alteration—Continued. Page. 

Oxidation—Continued. 

Vein oxidation. 198 

Structure of the oxidized veins. 199 

Oxidizing processes. 199 

Influence of oxidation on gold, silver, and tellurium. 203 

Secondary sulphide enrichment. 204 

Chapter X.—The ore shoots. 205 

Dimensions and pitch of the shoots. 205 

General form of the shoots. 206 

Relation to surface. 207 

Relation to country rock. 208 

Relation to intersections. 209 

Other factors. 213 

Influence of depth. 214 

Chapter XI.—Genesis of the deposits and practical conclusions. 217 

Origin of the ores. 217 

Composition of the vein-forming waters. 217 

General statement. 217 

Silica. 217 

Fluorides. 218 

Chlorides. 219 

Sulphates. 220 

Carbonates. 221 

Hydrocarbons. 221 

Hydrogen sulphide. 222 

Iron. 222 

Calcium and magnesium. 222 

Alkali metals. 222 

Tellurium and gold. 223 

Relative quantity of sulphides. 225 

Conclusions. ' . 225 

Depth at which deposition took place. 226 

Temperature of the solutions. 226 

Time of deposition. 226 

Source of the water. 227 

Mode of deposition. 228 

Future of the district. 231 

Chapter XII.—Underground water. 233 

I ntroduction. 233 

Original water surface. 233 

Tunnel drainage. 235 

Conditions of water storage. 238 

Source of the water. 238 

Effect of drainage on water level. 239 

Future drainage. 246 

Chapter XIII.—Underground gases and temperature. 252 

Subterranean gase^. 252 

General statement. 252 

Composition of air. 252 

Distribution and mode of occurrence. 253 

Physical characteristics and composition. 254 

Physiological effects. 256 

Conditions of occurrence. 256 






















































CONTENTS. 


IX 


Chapter XIII.—Underground gases and temperature—Continued. Page. 

Subterranean gases—Continued. 

Origin of the gas. 257 

Remedial measures. 258 

Carbon dioxide and nitrogen in other mining districts. 258 

Detailed observations at Cripple Creek mines. 260 

Eastern part of the district. 260 

Eclipse mine. 260 

Elkton mine. 260 

Moose mine. 260 

Last Dollar mine. 261 

Modoc mine.,.. 261 

Blue Bird mine. 261 

Wild Horse mine. 261 

Logan and Orpha May mines. 261 

Doctor-Jackpot mine. 261 

El Paso and C. K. & N. mines. 262 

Pointer and Mint mines. 262 

Poverty Gulch. 262 

Conundrum mine. 262 

Ophelia tunnel. 269 

Copper Mountain. 269 

Underground temperature. 269 

Part II.—Detailed Descriptions of Mines. 

Chapter I.—Mines north and east of the town of Cripple Creek. 271 

Mineral Hill. 271 

Carbonate Hill. 271 

Poverty Gulch. 271 

C. O. D. mine. 272 

Prospects near the C. O. D. 272 

Gold King mine. 273 

Mollie Kathleen mine. 274 

Gold Pass dike. 275 

Abe Lincoln mine.*. 276 

Introduction. 276 

Underground development. 276 

Geological features. 276 

Lode systems. 277 

Character of ore. 278 

Pay shoots and lode structure. 278 

Underground water. 279 

Rhyolite Mountain. 279 

Geological features. 279 

Prospects on Rhyolite Mountain. 279 

Fluorine mine. 280 

Red Mountain.. 280 

Galena mine. 280 

Area between Cameron and Gillett. 281 

Geological features. 281 

Sunshine mine. 281 

Deposits near Gillett. 282 


















































X 


CONTENTS. 


Page. 

Chapter I.—Mines north and east of the town of Cripple Creek—Continued. 

Globe Hill. 283 

Geological features... 283 

Deerhorn mine. 284 

Plymouth Rock mine. 285 

Ironclad mine . [: ... 285 

Hoosier mine._.... .1_ 286 

Head of Squaw Gulch. 287 

North slope of Ironclad Hill... 288 

Jerry Johnson mine..v.. 288 

W. P. H. mine. . .... 288 

Damon mine.■... 289 

Chapter II.—Mines of Gold Hill. 291 

General introduction. 291 

Anchoria-Leland, Jefferson, Geneva, and Half Moon mines. 291 

Introduction. 291 

Production and dividends."...I... 292 

Underground development. 292 

Geological features. 293 

Lode systems. 294 

Character of ore. 294 

Pay shoots and lode structure. 295 

Underground water .._*.*.*_.... 297 

Moon-Anchor, Midget, and Conundrum mines. 297 

Introduction._. 297 

Production. 298 

Underground development. 298 

Geological features. 301 

Lode systems. 302 

Character of ore. 303 

Pay shoots and lode structure..-.. 304 

Underground water. 306 

E. Porter Gold King mine. £ . 306 

Mint, Pointer, Accident, and Red Spruce mines. 306 

Introduction. 306 

Underground development.=.... 306 

Geological features. 307 

Lode systems. 307 

Character of ore. 307 

Pay shoots and lode structure. 308 

Underground water. 308 

Anaconda mine. 308 

Introduction. r . 308 

Production.,. 309 

Underground development.i— 309 

Geological features..-. 309 

Lode systems. 309 

Character of ore. 311 

Pay shoots and lode structure. 311 

Underground water. 313 

Gas. 313 

Caledonia mine. 313 

Cardinal shaft. 313 






















































CONTENTS. 


XI 


Chapter III.—Mines of Raven and Guyot hills_ 

General introduction. 

Doctor-Jackpot and Morning Glory mines 

Introduction.. 

Underground development. 

Geological features. 

Lode systems. 

Character of ore. 

Pay shoots and lode structure. 

Underground water. 

Mary McKinney mine.. 

Introduction. 

Underground development.. 

Geological features. 

Lode systems. 

Pay shoots and lode structure. 

Character of ore. 

Undergrourfd water. 

Peggy mine. 

Katinka mine. 

Elkton mine. 

Introduction. 

Production and dividends. 

Underground development. 

Lode systems. 

Geological features... 

Form and structure of the ore bodies . 

Character of ore. 

Underground water. 

Moose mine. 

Introduction. 

Production. 

Underground development. 

Geological features. 

Lode systems. 

Character of ore. 

Pay shoots and lode structure. 

Underground water. 

Gas. 

Joe Dandy mine. 

New Haven mine. 

Mary Ann mine. 

Mohawk Belle mine. 

Ida May mine. 

Chapter IV.—Mines of Beacon Hill. 

General introduction. 

El Paso mine. 

Introduction. 

Production. 

Underground development. 

Geological features. 

Lode systems. 

Character of ore. 

Pay shoots and lode structure. 


I’age. 

314 

314 

314 

315 
315 
317 

317 

318 

319 
321 
321 

321 

322 
322 
324 

327 

328 

329 

330 

330 

331 
331 
331 

331 

332 

333 
336 
339 
341 
341 

341 

342 
342 

342 

343 

343 

344 

345 
345 
345 
345 
347 
347 
347 
349 
349 
349 
349 
349 

349 

350 

351 
353 
353 
























































XII 


CONTENTS 


Chapter IV.—Mines of Beacon Hill—Continued. 

C. K. & N. and Old Gold mines. 

Introduction... 

Production. 

Underground development. 

Geological features. 

Lode systems. 

Character of ore. 

Pay shoots and lode structure. 

Underground water. 

Gas. 

Prince Albert, Gold Dollar, Zoe, and Mabel M. mines 

Introduction. 

Underground development. 

Geological features. 

Lode systems. 

Character of ore. 

Pay shoots and lode structure. 

Underground water. 

Chapter V.—Mines of Bull Hill. 

General introduction. 

War Eagle and Ramona mine. 

Ramona No. 2 mine. 

Sheriff mine.<. 

Bogart mine. 

Happy Year mine. 

New York tunnel.. 

Albany tunnel.. 

Wild Horse mine. 

Londonderry mine. 

Gold Sovereign mine. 

Trilby mine. 

Trail mine. 

Dante mine.. 

Blue Bird mine. 

Dexter mine. 

Last Dollar mine. 

Production and development. 

Geological features. 

Lode systems. 

Ores. 

Pay shoots . 

Details of the Last Dollar vein system. 

Details of the Modoc system. 

Modoc mine. 

Production and development. 

Geological features. 

Vein system... 

Ore. 

Ore shoots. 

Rubie mine... 

Stratton properties on Bull Hill_„•. 

Situation and development.. 

Water and gas. 


Page. 

355 

355 

355 

355 

356 
356 

356 

357 

368 

358 
358 
358 

358 

359 

360 
360 

360 

361 

362 
362 

362 

363 

364 

365 
365 

365 

366 

366 

367 
367 

369 

370 
370 

372 

373 

374 
374 

374 

375 
375 
375 
375 

377 

378 
378 
378 

378 

379 
379 

379 

380 
380 
380 























































CONTENTS 


XIII 


Chapter V.—Mines of Bull Hill—Continued. 

Stratton properties on Bull Hill—Continued. 

Geological features. 

Vein systems. 

Logan vein. 

Orpha May vein. 

Mineral Rock vein. 

Shurtloff vein. 

Los Angeles vein. 

Mines near Cameron. 

Pinnacle mine. 

Block 8, school section 16. 

Block 10, school section 16. 

Chapter VI.—Mines between Altman and Goldfield. 

Isabella lode system. 

Victor mine. 

Production and development. 

Geological features. 

Vein system. 

Occurrence of the ore. 

Isabella mine. 

Production and development. 

Geological features. 

Veins ... 

Oxidation. 

Ore and vein structure. 

Ore shoots. 

Mines between the Victor and Vindicator vein systems 

General relations. 

Empire No. 2 vein. 

Production and development. 

Geological features. 

The vein. 

Ore shoots. 

Pharmacist vein. 

Empire State mine. 

Pinto mine. 

Introduction. 

Geological features. 

Vein systems. 

Burns mine. 

Wrockloff mine. 

Pharmacist mine. 

Introduction. 

Vein systems. 

Character and occurrence of the ore. 

Zenobia mine. 

Mercer mine. 

Murphy mine. 

Pueblo mine. >--- - 

Wacu Weta mine. 

Deadwood mine. 

Production and development.,. 

Geological features. 

Vein systems. 


Page. 


381 

381 

381 

382 

382 

383 
383 
383 

383 

384 

386 

387 
387 
387 
387 
387 

387 

388 

389 
389 

389 

390 

391 

391 

392 

393 
393 
393 

393 

394 

394 

395 
395 

395 

396 
396 

396 

397 
397 
399 
399 

399 

400 

400 

401 

402 

403 

403 

404 
404 
404 
404 
406 























































XIV 


CONTENTS. 


Chapter VI.—Mines between Altman and Goldfield—Continued. Page. 

Mines between the A'ictor and Vindicator vein systems—Continued. 

Trachyte mine. 406 

Pearl mine...... 406 

Deadwood No. 2 mine. 406 

Introduction. ;;1 . 406 

Geological features. 406 

Character and occurrence of the ore. 407 

Ore shoots. 407 

Delmonico mine. 408 

Vindicator lode system... 408 

Findley and Shurtloff mines. 409 

Production and development. 409 

Geological features. 409 

Veins. 410 

Ore shoots. 411 

Hull City mine. 412 

Production and development. 412 

Geological features. 412 

The veins and their ore. 413 

Ore shoots. 414 

Vindicator mine. 415 

Production and development. 415 

Water level and oxidation .. ^. 416 

Geological features. 416 

Vein systems. 417 

Ore shoots. 418 

Details of Nos. 1, 2, and 3 veins. 420 

Details of Wallace vein. 421 

Details of southern veins. 422 

Christmas mine. 422 

Lillie mine. 424 

• Golden Cycle and Theresa mines. 424 

Production and development. 424 

Geological features. 426 

The veins in general. 427 

Oxidation. 428 

Vein structure and ore. 428 

Ore shoots. 429 

Chapter VII.—Mines of Battle Mountain (east group). 430 

General introduction. 430 

Portland mine. 430 

Introduction. 430 

Production and dividends. 431 

Underground development. 431 

Geological features. 433 

Lode systems. 439 

Character of ore. 442 

Pay shoots and lode structure. 443 

Value of the ore. 448 

Underground water. 449 

Stratton’s Independence mine. 449 

Introduction. ' 449 

Production and dividends. 451 

Underground development. 452 























































CONTENTS. 


XV 


Chapter VII.—Mines of Battle Mountain (east group)—Continued. Page. 

. Stratton’s Independence mine—Continued. 

Lode systems. 452 

Geological features. 457 

Pay shoots and lode structure. 461 

Value and character of the ore. 464 

Underground water. 465 

Chapter VIII.—Mines of Battle Mountain (west group) and outlying prospects. 466 

Strong mine. 466 

Introduction. 466 

Production. 466 

Underground development. 466 

Lode systems. 466 

Geological features. 467 

Form and structure of the ore bodies. 469 

Character of ore. 470 

Underground water. 470 

Granite mine. 471 

Introduction. 471 

Production. 471 

Underground development. 471 

Lode systems. 471 

Geological features. 472 

Character of ore.-. 473 

Form and structure of the ore bodies. 474 

Underground water. 475 

Monument mine... 475 

Introduction. 475 

Underground development. 475 

Lode systems. 475 

Geological features. 476 

Form and structure of the ore bodies. 476 

Character of ore. 476 

Dillon mine. 476 

Introduction. 476 

Underground development. 477 

Lode systems. 477 

Geological features. 477 

Form and structure of the ore bodies. 477 

Ajax mine. 478 

Introduction. 478 

Underground development. 478 

Lode systems. 478 

Geological features. 479 

Form and structure of the ore bodies. 481 

Character of ore. 483 

Dead Pine mine. 484 

Introduction. 484 

Underground development. 484 

Lode systems. 485 

Geological features.. 485 

Form and structure of the ore bodies. 486 

Character of ore. 487 

Value of the ore. 487 






















































XVI CONTENTS. 

Chapter VIII.—Mines of Battle Mountain (west group) and outlying prospects—Continued. Page. 

Gold Coin mine. 487 

Introduction. 487 

Underground development. 488 

Lode systems. 488 

Geological features. 490 

Form and structure of the ore bodies. 491 

Character of ore. 493 

Underground water. 494 

Sunset-Eclipse mine. 494 

Carbonate Queen mine. 495 

Big Bull, Brind, and Straub mountains and Grouse Hill..•. 495 

Lower Cripple Creek. 496 














S 


ILLUSTRATIONS. 


/ Uajjft 

Plate I. Topographical map of Cripple Creek district. In pocket. 

II! Geological map of Cripple Creek district, with sections. In pocket. 

III. Plan of principal underground workings at Cripple Creek. In pocket. 

IV. ’- A, Cripple Creek, looking west from Gold Hill; B, Cripple Creek, looking northeast. 18 

VY Plan of part of the underground workings of the Battle Mountain mines. 26 

VI. A, Town of Victor, from Squaw Mountain; B, Battle Mountain mines, from Squaw 

Mountain. 34 

VII. A, B, C, D, Photomicrographs of phonolite. 60 

VIII. A, B, C, D, Photomicrographs of latite-phonolite, syenite, and trachydolerite. 82 

IX: .4, B, C, Photomicrographs of trachydolerite, monchiquite, and vogesite. 94 

X.' Diagram showing composition of rocks of Cripple Creek. 112 

XI. Section across the Cripple Creek district from the Abe Lincoln mine to Stratton’s 

Independence mine. 148 

XII. Plan of the principal fissures of the Cripple Creek district, shown as intersecting a 

plane 9,500 feet above sea level. 154 

XIII. A, B, Vein structure, Conundrum mine. 160 

XIV. v A, B, Vein structure, Portland mine. 162 

XV/M, B, Vein structure, Portland mine. 164 

XVI/ A, Vein structure, surface workings showing Anaconda vein; B, Vein structure, basic 

dike, Portland mine. 166 

XVII! A, B, C, D, E, Photomicrographs of ores. 180 

XVIII! A, B, Photomicrographs of ores. 186 

XIX. Diagram showing the shape and vertical range of some of the principal ore shoots of 

the Cripple Creek district. 206 

XX. Diagram showing the water level at various times in the principal mines of Cripple 

Creek. 242 

XXI.' .4, Rhyolite Mountain from summit of Bull Hill; B, Pikes Peak and the town of 

Gillett from the summit of Bull Hill. 280 

XXII! A, North slope of Gold Hill; B, West slope of Raven Hill, showing the Doctor- 

Jackpot and Morning Glory group of mines. 292 

XXIII. Elkton mine and south slope of Raven Hill. 332 

XXIV/ A , The El Paso, C. K. & N., Old Gold, and Henry Adney mines on Beacon Hill; 

B, Beacon and Grouse hills from Raven Hill. 350 

XXV. A, South slope of Bull Hill as seen from Squaw Mountain; B, Bull Cliff and town of 

Independence. 362 

XXVI. A, Golden Cycle mine and part of town of Goldfield; B, Stratton’s Independence 

and Strong mines. 416 

XXVII. The Portland mine from the south. 430 

XXVIII. 1 Geological map of the 500-foot level of the Portland mine. 434 

XXIX. Vertical section through the Burns shaft, Portland mine. 440 


13001—No. 54—06-2 


XVII 
































XVIII 


ILLUSTRATIONS. 


Page. 

Fig. 1. Index map showing situation of Cripple Creek district. 12 

2. Geological section across Grouse Hill and Straub Mountain. 37 

3. Sections showing possible outline of the Cripple Creek volcanic cone at the close of the 

volcanic epoch. 39 

4. Structure of La Bella vein, Golden Cycle mine, level 9. 160 

5. Legal Tender vein, Golden Cycle mine, level 10. 160 

6. Veins in Last Dollar mine. 161 

7. Section of Howard flat vein, Anaconda mine, adit level. 161 

8. North face of No. 8 Captain vein, Portland mine, level 6. 162 

9. Sheeted zone and “flats” of the Apex vein, Ajax mine. 162 

10. Section of part of Blue Bird vein, level 13. 163 

11. Structure of the Blue Bird vein, level 9. 163 

12. Sketch section across expansion of vein on level 7, Elkton mine, looking north. 178 

13. Local structure in C. K. & N. vein. 181 

14. Diagram illustrating use of terms in descriptions of ore bodies. 206 

15. Cross section and longitudinal section of pay shoot in Prince Albert mine. 208 

16. Longitudinal section of the El Paso vein. 209 

17. Diagram of veins and stopes in upper levels of Damon mine. 210 

18. Stereogram of ore shoots on the Pinto dike and Pharmacist vein, in the Pinto and 

Wrockloff mines. 211 

19. Plan showing occurrence of ore bodies at intersection of sheeted zone and phonolite 

dike in Dead Pine mine. 212 

20. Diagrammatic plan showing occurrence of ore body in granite on level 5, Ajax mine .. 212 

21. Plan of an ore body in granite, level 4, Ajax mine. 213 

22. Diagram showing relation between the subsidence of the water in the Elkton mine and 

the outflow from the El Paso tunnel. 236 

23. Diagram showing probable extent of area practically affected by drainage tunnels into 

Beacon Hill. 250 

24. Longitudinal section showing ventilation in the Conundrum and Midget mines. 263 

25. Plan of level 1 of Anchoria-Leland mine and of adjacent levels of the Jefferson, Geneva, 

and Half Moon mines. 293 

26. Longitudinal section of the Chance vein, Anchoria-Leland mine. 295 

27. Longitudinal section of Maloney vein, Anchoria-Leland mine. 296 

28. Geological plan of portion of level 3 of the Conundrum, level 7 of the Midget, and level 

6 of the Moon-Anchor mines. 299 

29. Diagram showing relative position of levels in Conundrum and Midget mines. 300 

30. Plan of adit level, Anaconda mine. 310 

31. Plan of parts of underground working at Doctor-Jackpot and Morning Glory mines_ 316 

32. Plan of the veins of the Mary McKinney mine, level 4. 323 

33. Generalized longitudinal section of the Mary McKinney mine. 325 

34. Plan showing principal dikes and fissures on level 7 of the Elkton mine. 332 

35. Generalized longitudinal section of the Elkton mine. 333 

36. Plan of ore body in granite, Elkton mine, level 4. .... . 338 

37. Plan of level 15 of the Moose mine.. 343 

38. Longitudinal section of the Moose mine.•. 344 

39. Plan of level 2, El Paso mine. 350 

40. Diagrammatic northwest-southeast section across Beacon Hill, through El Paso and Zoe 

shafts. 351 

41. Sketch plan of level 4, Gold Dollar mine. 359 

42. Vein systems in Whisper and Dante mines, chiefly on level 4. 371 

43. Vein system of Last Dollar mine, on levels 5, 8, 10, and 12. 376 

44. Map of the Victor and Isabella vein s) 7 stems. 388 

45. Longitudinal projection of the Buena Vista and Cheyenne veins of the Isabella mine.. 390 












































ILLUSTRATIONS. XIX 

Page. 

b'ic;. 46. Cross section of the Buena Vista and East veins at the Lee shaft, Isabella mine. 390 

47. Vein system on level 11, Bindley mine. 410 

48. Cross section of Findley vein through Findley shaft, looking northwest. 410 

49. Map of fourth (550-foot) level, Hull City mine... 413 

50. Cross section of Hull City mine, looking northwest. 414 

51. Map of level 12, Vindicator mine..... 419 

52. Cross section of Vindicator mine along line L-J on plan, looking northwest. 420 

53. Cross section through Christmas shaft, looking northwest. 423 

54. Cross sections of the Lillie vein, perpendicular to the plane of shafts 1, 2, and 3. 425 

55. Map of level 6, Golden Cycle mine. 428 

56. Plan of the'Portland mine.... 432 

57. Generalized longitudinal projection through the Portland mine. 433 

58. Stereogram of Anna Lee ore chimney. 447 

59. Map of level 4, Stratton’s Independence mine. 454 

60. Map of level 8, Stratton’s Independence mine. 455 

61. General north-south section through Stratton’s Independence mine... 458 

62. Section through Stratton’s Independence mine. 459 

63. North-south section through the Ajax shaft. 479 

64. Plan of level 7, Gold Coin mine. 488 


























SYNOPSIS OF PART I. 

CHAPTER I.—INTRODUCTION. 

The Cripple Creek gold deposits, discovered in 1891, were investigated by Messrs. 
Cross and Penrose, of the United States Geological Survey, in 1894. The present 
reexamination was requested by citizens of Colorado, and has been carried out 
under the financial cooperation of the State with the Federal Survey. It has 
involved complete revision of the topographic map of the district used as a base by 
Cross and Penrose, the running of a line of accurate levels from Colorado Springs to 
Cripple Creek, remapping of the geology, and a thorough stud}^ of the extensive 
mine workings opened during the past ten years. Due acknowledgment is made of 
• the cordial assistance rendered by mining men, and a list is given of the important 
publications concerning the geology or mines of the district. 

CHAPTER II.—GENERAL GEOLOGY. 

Results of first geological survey of the district .—The Cripple Creek hills lie near 
the eastern border of a much dissected plateau which slopes gently westward for 40 
miles from the southern end of the Colorado Range, dominated by Pikes Peak, to 
the relatively low hills connecting the Mosquito and Sangre de Cristo ranges. The 
prevailing rocks of this plateau are granites, gneisses, and schists. The granites 
inclose masses of Algonkian quartzite and are therefore post-Archean; but they are 
older than the only Cambrian sediments known in Colorado. During Tertiary time 
volcanic eruptions broke through these ancient rocks at several points and piled 
tuffs, breccias, and lavas upon the uneven surface of the plateau. The eruptive 
rocks of the Cripple Creek district are the products of one of the smaller isolated 
volcanic centers of this period, a center characterized by the eruption of phonolite, 
which does not occur elsewhere in this general region. 

The most voluminous products of the Cripple Creek volcano now preserved are 
tuffs and breccias. They occupy a rudely elliptical area in the center of the district, 
about 5 miles long in a northwest-southeast direction and about 3 miles wide. 
According to Cross, these breccias and tuffs rest in part upon an earlier flow of 
andesite, but mainly upon an unevenly eroded surface of the granites and schists. 
The breccia is much indurated and altered, but was thought by him to consist 
mainly of andesitic fragments. The most characteristic massive rock of the Cripple 
Creek volcano is phonolite. It occurs as dikes and masses in the breccia and in the 
surrounding granitic rocks. 

The general succession of igneous rocks, according to Cross, is as follows: The 
earliest rocks were andesites containing some orthoclase. Then came a series of 
allied phonolitic rocks, rich in alkalies and moderately rich in silica, together with 


l 


9 


GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


some andesites. Among them are trachytic phonolite, nepheline syenite, syenite 
porphyry, phonolite, mica andesite, and pyroxene andesite. Phonolite was erupted 
at several periods. The nepheline syenite he considered as probably younger than 
the trachytic phonolite. At the close were intruded a small number of narrow 
dikes of basic rocks, the so-called basalts, which contrast very markedly with the 
phonolite. 

Modification of earlier results .—The present investigation indicates some neces¬ 
sary modifications of the earlier report in the way of stronger emphasis on the 
intimate genetic relationship of the rocks. The “phonolite,” “nepheline syenite,” 
“trachytic phonolite,” “syenite porphyry,” and “andesites” of Cross are all very 
closely related and have been found to be in most cases so closely connected by 
intermediate types as to be practically inseparable. None of the massive rocks 
can properly be called andesite, and although it can not be affirmed that andesitic 
fragments are entirely absent from the usually much-altered volcanic breccia, the 
term “andesitic breccia” does not seem applicable to this formation as a whole, 
which is composed chiefly of fragments of phonolitic rocks accompanied locall}' by 
much granite, gneiss, or schist detritus. 

None of the massive rocks erupted from the Cripple Creek volcanic center and 
now preserved in the district show any evidence of having been surface flows. They 
are for the most part intrusive porphyries, ranging in texture, however, from the 
granular so-called nepheline syenite near the town of Independence to the nearly 
aphanitic phonolite of the smaller dikes and sheets. Most of them come under the 
designations phonolite, latite-phonolite, trachvdolerite, and syenite. 

While the breccia may in a few places rest upon an uneven surface of erosion, 
it occupies in the main a steep-walled chasm extending to unknown depth and 
constitutes a typical volcanic neck. 

The rhyolite of Grouse Hill and Straub Mountain is intrusive into the associated 
grits of this part of the district. The grits can not, therefore, be correlated with the 
Miocene High Park lake beds, and this modifies somewhat the argument from which 
Cross deduced the probable Miocene age of the Cripple Creek volcano. 

Structure of the district .—The pre-Cambrian crystalline complex which forms 
the general plateau of the region was perforated by a volcanic explosion. The deep 
pit thus formed was filled with a breccia composed of fragments of phonolite and 
allied rocks and of granite, gneiss, and schist. The walls of the pit are steep and 
rather irregular. They exhibit local bench-like flattening and in some places over¬ 
hang the breccia. The breccia occasionally shows an indistinct and nonpersistent 
bedding or banding and its constituent particles vary widely in size.' 

The breccia is cut by intrusive bodies of syenite and trachyphonolite, these 
two rocks showing frequent gradations from one to the other. The intruded bodies 
are usually of very irregular shape and have been peripherally shattered to such a 
degree that their contacts with the breccia are very obscure. These rocks generally 
form stock-like masses or thick, irregular sheets. The breccia is also cut by numer¬ 
ous dikes of phonolite, and this rock forms intrusive sheets and masses of consider¬ 
able size in the prevolcanic crystalline rocks. Beacon Hill is a conspicuous example 
of a plug of phonolite in granite. 


SYNOPSIS OF PART I. 


3 


4 


CHAPTER III.-DESCRIPTION AND PETROLOGY OF THE METAMORPHIC AND IGNEOUS 

ROCKS. 

The rocks of the district are chiefly of metamorphic and igneous origin. Two 
broad divisions may readily be made: (1) The pre-Cambrian metamorphic and 
igneous basement complex and (2) the products of the Tertiary Cripple Creek 
volcano. 

The metamorphic rocks comprise a much foliated quartz-muscovite-fibrolite 
schist, which was probably derived from sedimentary rocks, and a biotite gneiss 
derived from a granitic rock. Of the ancient igneous rocks two groups may be dis¬ 
tinguished. The first group comprises three varieties of granite, which are closely 
related in composition and have been named, in order of probable age, the Pikes 
Peak type, a coarse-grained quartz-microcline-biotite granite, the most abundant 
rock of the whole region; the Cripple Creek type, a finer-grained rock of similar 
composition, and the Spring Creek type, of medium grain, composed mainly of 
quartz and orthoclase, with a little muscovite. An interesting feature of these 
granites is the presence of fluorite, which is probably original. The second group 
includes the products of differentiation from an olivine-syenite magma. The pre¬ 
dominant rock is composed of microperthite, diallage, and olivine, with accessory 
quartz. The other rocks are an olivine gabbro, with a doleritic contact phase 
which establishes a close relation to the olivine-bearing diabase dikes which cut 
the granite in many parts of the area. 

Tertiary volcanic rocks afford a striking example of the chemically related 
products of a single center of eruption. The most abundant and characteristic of 
these rocks is phonolite. Next in importance is latite-phonolite, which consists 
essentially of soda-orthoclase, sodic plagioclase, sodalite, nosean, analcite, legirine- 
augite, and augite. A syenite rich in alkalies and containing orthoclase, augite, 
and hornblende as essential constituents is the third member. A trachydolerite 
composed of plagioclase, orthoclase, analcite, augite, and biotite is the least abun¬ 
dant of the rocks occurring in irregular intrusive masses. Three varieties of rocks 
occur as dark basic dikes. These are (1) trachydolerite, (2) vogesite, and (3) 
monchiquite. 

These Tertiary rocks are mentioned above in the order of decreasing silica. In 
spite of wide variations in texture, mineralogical character, and chemical compo¬ 
sition an intimate connection or consanguinity exists between all these rocks, of 
which some of the manifestations are the almost invariable appearance of ortho¬ 
clase and analcite as the final products of crystallization and the remarkably 
constant ratio of silica to alumina. All these volcanic rocks have unquestionably 
been derived from the same magma and constitute an excellent example of mag¬ 
matic differentiation within a confined petrographic province. 

Owing to simple structural relations the composition of the average rock of 
the Cripple Creek volcano can be computed and is found to be close to that of 
phonolite. 


4 


GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


CHAPTER IV.—GENERAL MINERALOGY OF THE DISTRICT. 


A list of well-established vein minerals includes the following species: 


Calaverite. 

Sylvanite. 

Krennerite. 

Pyrite. 

Molybdenite, 

Sphalerite. 

Galena. 

Stibnite. 


Tetrahedrite. 

Hubnerite. 

Quartz. 

Chalcedony. 

Opal. 

Fluorite. 

Calcite. 

Dolomite. 


Rhodoehrosite, 

Barite. 

Celestite. 

Wavellite. 

Adularia. 

Sericite. 

Roscoelite. 


Among the more important secondary minerals due to oxidation are: 

Gold. Psilomelane. Gypsum. 

Emmonsite. Molybdite. Chalcanthite. 

Limonite. Alunite. Epsomite. 


CHAPTER V.-HISTORY AND TECHNOLOGY OF THE GOLD DEPOSITS. 

Earlier work. —The excellent work of R. A. F. Penrose, jr., was done at a time 
when there were no deep workings in the district. That his results should require 
some slight modification in the light of present facilities for investigation was to 
be expected. 

History of mining development. —Ore found by Robert Womack in Poverty 
Gulch drew E. M. De la Yergne and T. F. Frisbee to the district in December, 1S90. 
They returned in February, 1891, and recorded the first mining location. On July 
4 of the same year W. S. Stratton located the Washington and Independence claims, 
and in the rapid development of the district that followed the Independence mine 
soon attained great prominence. It was rivaled, however, by the Portland, now 
the largest mine in the district. Two railroads were completed into the district 
in 1893, and a third in 1901. There have been two periods of depression due to 
labor strikes, one in 1894 and another in 1903-4. The most important recent event 
in the history of the district was the opening of the El Paso tunnel in 1903, enabling 
several of the mines to extract ore previously below the water level. 

Production. —The district has produced, to the end of 1905, $124,415,022 in 
gold and 646,193 fine ounces of silver, the maximum production having been reached 
in 1900. 

Mining. —The ore is broken by overhand stoping and is usually hoisted by 
steam through vertical shafts. It is generally screened, the screenings as a rule 
constituting the richest part. The coarse ore is washed and hand sorted. The 
total cost of mining, including development and sorting, is probably nowhere less 
than $8 per ton. 

Sampling .—The district is well provided with sampling works, and through 
these nearly all the ore passes in its course from mine to reduction works. The 
sampling charges, exclusive of freight, range from 60 cents to $1 per ton. 

Processes of reduction.— Probably about one-sixth of the tonnage of ore mined 
at Cripple Creek goes to the smelters at Pueblo and Denver. This is the richest 
ore. The balance of the product is treated in chlorination and cyanide mills at 


SYNOPSIS OF PART I. 


5 


Florence, Colorado City, and elsewhere. In 1904 the charges for treatment at the 
mills ranged in the lowest schedule issued from $5.50 per ton for halt-ounce ore to 
$9 per ton for 3 to 5 ounce ore. This included freight from mine to mill. 

Labor conditions .—The minimum wages for ordinary miners are $3 for an eight- 
hour day. Conditions of work and living are good, but the district has suffered 
from two serious conflicts between mine owners and miners. 

Financial conditions .—While there are several large companies operating in 
the district, many small mines are under individual ownership, and there is much 
leasing, with royalties ranging from 15 to 35 per cent of the net returns. A tend¬ 
ency exists to organize companies at capitalizations greatly in excess of the prob¬ 
able value of the prospects which it is proposed to develop. Very few companies 
have been organized with less than $1,000,000 capital, and very few mines have 
yielded the amount of their capitalization in dividends. The fascination of a min¬ 
ing venture tempts investors to accept a rate of interest on their capital which is 
lower than it should be when the uncertainties of ore bodies and the usual limited 
life of a mine are taken into consideration. The costs of mining and treatment at 
Cripple Creek are high and do not always compare favorably with those prevailing 
in other districts that labor under no greater disadvantages. 

Extent of productive territory. —There is nothing in the history of the district 
since 1894 warranting any extension of the bounds of the productive territory as 
then known. All the important mines lie within a circle of 6 to 7 miles in diameter. 

CHAPTER VI.-PRELIMINARY REVIEW OF THE MINING INDUSTRY. 

Distribution. —In Poverty Gulch, near Cripple Creek, are the Abe Lincoln, 
Gold King, and C. O. D. mines. On Globe Hill, east of the town, are numerous 
properties belonging to the Stratton estate. Gold Hill, southeast of Cripple Creek, 
contains the Anchoria-Leland, Moon-Anchor, Half Moon, Midget, Conundrum, 
and other mines. Near the town of Anaconda are the Anaconda, Doctor-Jackpot, 
Morning Glory, and Mary McKinney mines. Around the phonolite plug of Beacon 
Hill are the El Paso, C. K. & X., Gold Dollar, Prince Albert, and many smaller 
mines. On the south slope of Raven Hill are the Elkton and Moose mines. 

On the east and southeast side of Blue Hill a very important belt of mines, 
extending from Altman through Independence to Goldfield, includes the Isabella, 
Victor, Pharmacist, Zenobia, Findley, Hull City, Vindicator, Lillie, Golden Cycle, 
Logan, Orpha May, Blue Bird, Last Dollar, and other well-known properties. 

On the south slope of Battle Mountain and extending into Victor is the great 
group of mines embracing the Portland, Stratton’s Independence, Strong, Ajax, 
Granite, Dead Pine, Gold Coin, and others. 

Extent of underground development. —The productive part of the district con¬ 
tains over 20 shafts more than 1,000 feet in depth and is intersected by very numer¬ 
ous and extensive drifts and crosscuts. 

Placers. —These were never very extensive, although they produced a fair 
amount of gold in early days. There is probably still ground on the southwest 
slope of Mineral Hill which would pay were water available for washing. 


6 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

CHAPTER VII.-STRUCTURE OF THE GOLD DEPOSITS. 

Principal types of deposit .—The ore bodies are in almost all instances causally 
related to fissures. They comprise (1) lodes or veins and (2) irregular replacement 
bodies, usually in granite. These two types are not sharply distinct. All of the 
ore deposits are characterized by the narrowness of the fissures which gave passage 
to the ore-bearing solutions and by the comparatively small volume of material 
deposited in these fissures. 

Lode fissures .—These occur mainly within and near the volcanic neck, and 
have a rough radial plan. They are usually nearly vertical, although there are 
some notable examples of productive “flat veins.” Individual fissures rarely 
exceed half a mile in length, but some well-defined zones of Assuring are traceable 
for twice that distance. Some of the most productive fissures are less than 300 
feet in length. The persistence of a fissure down the dip is roughly proportional 
to the length of the same fissure. In general the fissures seem to be smaller and 
less abundant in depth than near the surface. 

Productive lodes occur in all the rocks of the district, with the possible excep¬ 
tion of the schist. They are most abundant in breccia and in granite. Many lodes 
follow phonolitic or basic dikes. 

The structure most characteristic of the Cripple Creek lodes is the sheeted 
zone, which occurs in various degrees of regularity and in widths ranging from a 
few inches to over 100 feet. The fissures of the zone are usually very narrow, 
although there are a few notable exceptions to this rule. Evidence of tangential 
movement or faulting along the fissures is rare. 

Intersections of one fissure zone by another are common and usually show no 
visible displacement. In general the fissures are not fault planes, although there 
are some exceptions to this statement. 

The fissures were probably formed about the same time as the intrusion of the 
basic dikes and represent a late phase of volcanic activity. They were probably 
opened under relatively light load by local compressive stresses due to a slight 
subsidence of the solidified breccia, and associated intrusive rocks forming the 
volcanic neck. 

CHAPTER VIII.-THE ORES. 

The characteristic feature is the occurrence of the gold in combination with 
tellurium and chiefly as calaverite. Native gold is present in the unoxidized ores 
only as a rarity. Pyrite is widely distributed in the country rock and also occurs 
in the veins, with tellurides. Galena, sphalerite, tetrahedrite, stibnite, and molyb¬ 
denite are sparingly present . Among the gangue minerals quartz, fluorite, and dolo¬ 
mite prevail; celestite is also often present, but is frequently changed into quartz. 
The ore occurs chiefly as filling of narrow fissures, and consequently the ores as 
mined have the approximate composition of the country rock. The average 
tenor of gold in the ores is about $30, or 1.5 ounces per ton, and at various mines 
ranges from 1 ounce up to 3 or 4 ounces. Ore with less than $12 per ton is rarely 
mined. Small amounts of ore with up to 2,500 ounces of gold per ton have been 
mined. The pyrite is rarely auriferous except when admixed with tellurides. 


SYNOPSIS OF PART I. 


7 


The ores contain on an average only about 1 ounce of silver to 10 ounces of gold. 
In some mines the proportion is very much less. Small shipments have been 
made of tetrahedrite ore rich in silver. 

The tenor of the ore as mined has decreased somewhat in the last ten years, 
but this is probably mostly due to lowered operating and reduction expenses. 

CHAPTER IX.-PROCESSES OF ALTERATION. 

Metasomatism in connection with vein formation .—During the vein-forming 
processes the rocks adjacent to veins have undergone a certain amount of alteration, 
and in case of the porous breccia this alteration has spread over large areas. The 
alteration is, on the whole, slight and involves a transformation of the dark silicates 
to carbonates, pyrite, and fluorite and a change of the feldspars and feldspathoid 
minerals into sericite and adularia. The latter mineral is characteristic of all the 
altered rocks, but especially of the so-called “granitic ore” of the Elkton, Ajax, 
Stratton’s Independence, and other mines. Calaverite develops in places by meta- 
somatic processes in breccia, gneiss, phonolite, and basic dikes, but its appearance 
in this form is rare, compared to its universal occurrence as fissure filling. Galena, 
zinc blende, and other sulphides sometimes appear as metasomatic products, but 
are not common. Chemically the process, when carried to completion, involves 
an almost entire loss of soda and a corresponding gain of potash. Small amounts 
of sulphur, carbon dioxide, and fluorine are introduced. The percentage of silica 
is slightly reduced, and lime and magnesia have often been partially removed. 
The course of the alteration, which is shown to have been produced by hot alkaline 
waters, is illustrated by several analyses. 

Oxidation .—The oxidation away from the vicinity of veins has not penetrated 
to great depths. Globe Hill is an exception, for here complete oxidation has affected 
the breccia to a depth of at least 800 feet below the surface. Along the veins 
oxidation extends far deeper, in some cases down to 1,200 feet below the surface. 
The water level originally stood at an elevation of about 9,500 feet, rising to 9,600 
or 9,700 feet under Bull Hill. In a general way the depth of oxidation along veins 
coincides with the depth of the water level. There are many exceptions; in the 
western part of the district unaltered tellurides may be found close to the surface, 
while in other cases complete oxidation extends for 200 or 300 feet below the water 
level. 

Oxidation tends to destroy the original structure of the vein and changes the ore 
to a brown, soft, and homogeneous mass. Oxidation tends also to transform tellu¬ 
rides into brown, spongy gold and tellurites, while sulphides are altered to various 
oxy-salts. The silicates are changed to kaolin, quartz, manganese dioxide, and 
limonite. The agent producing oxidation is atmospheric water percolating down¬ 
ward along the vein and the process continues until this water has lost its oxygen. 
The waters are acid, due to the sulphuric acid derived from pyrite. The results 
of oxidation are illustrated by several analyses. No evidence favoring the deposi¬ 
tion of secondary sulphides has been found. The tetrahedrite supposed by some 
to be of such origin is a primary vein mineral. 


I 


8 


GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


CHAPTER X.-THE ORE SHOOTS. 

As a rule the ore in the veins occurs as well-defined shoots similar to those of 
other gold veins; their limit in depth is ordinarily as well marked as their extent 
in a horizontal direction. In discussing the shoots the terms pitch length, stope 
length, breadth, and width or thickness are adopted and defined. 

The shoots are generally tabular, elongated bodies dipping at steep angles from 
the horizontal on the plane of the vein. The width varies from a few inches to 50 
feet, 4 to 5 feet being a common size. The stope length in an ordinary shoot varies , 
from 50 to 300 feet, and in rare cases attains 2,000 feet. The pitch is steep, ranging 
from 45° to 90° and is generally northward. An average of the pitch length in the 
large shoots would probably he 500 feet, but in a few shoots this dimension attains 
1,500 feet, and in others the total length of the shoot has not yet been ascertained. 
While the outline is sometimes equidimensional, or again wholly irregular, elongated 
forms with ratio between pitch length and breadth of from 14:1 to 5:1 prevail. 
When one shoot ceases in depth, another may be found below it upon the same or 
adjoining fissure. 

Absolute and truncated pitch lengths are distinguished. In the latter case 
the upper part of the shoot has been removed by erosion. 

The influence of countrv rock is very slight, as excellent shoots occur in granite, 
gneiss, breccia, latite-phonolite, phonolite, sj^enite, and basic dikes. Breccia is, on 
the whole, the most favorable rock on account of its porosity. The smaller ore 
shoots are very commonly found at intersections of fissures or fissure systems, but 
tins factor is by no means the only one nor the most important one. The largest 
shoots are entirely independent of intersections. 

There is no decrease in the value of the ore per ton in depth, but the quantity 
of ore available is distinctly less below the 1,000-foot level, irrespective of the eleva¬ 
tion of the surface. Difficulties of exploration and development may to some extent 
account for this, but another influencing factor is that in many cases the fissure 
system is less well developed in depth. In addition to this explanation it is likely 
that for reasons related to temperature and solubility precipitation of ore took place 
more abundantly nearer to the surface. 

CHAPTER XI.-GENESIS OF THE DEPOSITS AND PRACTICAL CONCLUSIONS. 

Or igin of th e ores .—The wa ters which deposit ed the Cripple Creek veins were hot 
alkaline solutions which contained the following compounds and ions either free or 
in various combinations: Si0 2 , C0 2 , Ii 2 S, C0 3 , S0 4 , S, Cl, F, Fe, Sb, Mo, V, W, Te, 
Au, Ag, Cu, Zn, Pb, Ba, Sr, Ca, Mg, Xa, K. We believe that at least some of the 
Si0 2 , S0 4 , Cl, Fe, Ba, Sr, Ca, Mg, Na, and K are derived from the volcanic rocks by 
leaching of waters, while the remaining metals, as well asC0 2 , II 2 S, S, and some SiO, 
and Cl, were more probably separated from intrusive cooling magmas at considerable 
depth and brought up as solutions in magmatic water given off in the same manner. 

It is concluded that the formation of the veins took place shortly after the intru¬ 
sion of the last basic dike. The temperature at the time of deposition was high, 
but the critical temperature of water was probably not exceeded. It is shown that 
the igneous rocks contain primary water and the conclusion is drawn that the magna 


SYNOPSIS OF PART I. 


9 


was correspondingly rich in water. The question of the derivation of the vein 
minerals is discussed; derivation by leaching from the granitic or the volcanic 
rocks by cold or hot atmospheric waters is shown to be improbable. The view 
that most of the water and most of the substances contained in the veins were 
given off by intrusive bodies slowly cooling at considerable depth and were forced 
up through the upper part of the volcanic mountain as soon as the formation of 
fissures allowed them to rise is considered more plausible. The waters ascended 
in the deeper part of the volcano with comparatively great velocity on the fewer 
fissures here available. Nearing the surface they spread through a larger space in 
a more complicated fissure system. The speed became checked and conditions for 
precipitation improved. Deposition and the chemical action of the country rock 
changed the composition of the solutions and a mingling with fresh ascending 
waters, possibly also with atmospheric waters, induced further precipitation. In 
this manner are explained the smaller amount of ore deposited in depth and the 
richness and abundance of ore nearer to the old surface. The portion of the volcano 
removed by erosion may have contained still richer deposits. 

Future of the district .—It is probable that the production of the district, while 
exhibiting fluctuations, will on the whole slowlv decline. New ore bodies will 
undoubtedly be discovered from time to time, and individual mines may be as 
profitable in the future as they have been in the past, or even more so. An increased 
output may be expected to follow each successful step in deep drainage. But 
existing conditions indicate that if the maximum production of $18,000,000 in 1900 
is to be surpassed the increase will be due to the ore bodies encountered in a zone 
within 1,000 feet of the present general surface. 

CHAPTER XII.-UNDERGROUND WATER. 

Although the annual precipitation at Cripple Creek is not heavy and the condi¬ 
tions for rapid run-off are unusually favorable, standing water was originally 
encountered in the mines at moderate depths. At the beginning of mining opera¬ 
tions the underground water surface stood at an elevation of about 9,500 feet in the 
western part of the district and, on an average, fully 100 feet higher in the eastern 
part. Several mines began pumping about the year 1895, but it was soon found 
that this mode of lowering the water was slow and costly. Attention was directed 
to tunneling, and the Ophelia tunnel was driven into Gold Hill at an elevation of 
9,268 feet. This tunnel drained the western part of the district until 1898, when 
the Standard tunnel, over 200 feet lower, tapped the phonolite of Beacon Hill and 
became the chief effluent. Finally the El Paso tunnel, with its portal at an eleva¬ 
tion of 8,783 feet, was driven under Beacon Hill in 1903 and has since been the main 
drainage outlet of the district. Prior to January 1, 1905, this tunnel is estimated 
to have discharged about 3,550,000,000 gallons or nearly 15,000,000 tons of water. 

The records of the pumping operations and tunnel projects show that the under¬ 
ground water is for the most part held within open fissures and cavities in the rocks 
of the volcanic neck. It is stored water, inclosed by the relatively impervious rim 
of granitic and schistose rocks that form the general Cripple Creek plateau, and has 
been supplied by the rain and snow that fell upon the surface of the district. 


10 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


Drainage and pumping have both shown that the underground water does not 
flow freely through the rocks in all directions. Neighboring mines in some cases 
show marked differences in water level, and the drainage tunnels on the west side 
of the district have but slightly benefited the mines on the east side. The behavior 
of the water shows that the unfissured breccia is practically almost impervious and 
that artificial drainage affects onty those parts of the district that are connected 
by fissures with the tunnel or shaft whence the water is drawn off. 

A movement is now in progress to begin a new drainage tunnel several hundred 
feet below the El Paso tunnel. Knowledge of the number of gallons of water cor¬ 
responding to a fall of 1 foot in the general reservoir would be of use in planning 
future operations. Mr. S. W. Mudd estimated that a discharge of 66,684,683 gallons 
corresponded to a general lowering of the water 1 foot. Mr. A. C. Jaquith estimated 
that in April, 1904, the discharge from the El Paso tunnel, corresponded to a lower¬ 
ing of the water 1 foot in the Elkton mine, was 34,839,775 gallons. The data on 
which Mr. Mudd’s estimate was based, however, are necessarily very incomplete 
and it is difficult to deduce, from the record of the Elkton, figures applicable to the 
entire area drained. The quantity of water drained for each foot of fall is likely to 
diminish with increase of depth, although it is probable that at a depth of 1,000 or 
1,500 feet below the El Paso tunnel open fissures and shattered zones in the breccia 
will still be sufficiently abundant to contain in the aggregate a large body of water. 

CHAPTER XIII.-UNDERGROUND GASES AND TEMPERATURE. 

Gases .—During the earlier years no unusual amounts of mine gases were noted, 
but as the workings deepened several properties began to be seriously inconven¬ 
ienced by a heavy gas which issued from the porous breccia or fine fissures. The 
principal sufferers have been the mines west of Battle Mountain and Bull Mountain. 
The gas has no smell or taste, but its presence is soon indicated by the fact that the 
candles refuse to burn and by several forms of physical distress among those who 
are obliged to work near the point where it issues.. A number of fatal cases of suffo¬ 
cation have occurred. The gas consists of a mixture of prevailing nitrogen with 8 
to 15 per cent of carbon dioxide and 5 to 10 per cent of oxygen. 

The gases carry much moisture and are warmer than the normal temperatures 
of the mines. The emanations are generally most copious when the barometric 
pressure is low, but they also exhibit fluctuations that are apparently independent 
of the state of the barometer. The gases are believed to be the last exhalations of 
the extinct Cripple Creek volcano. Probably the only effective way of combating 
the evil is by working under an air pressure slightly above the normal. 

Underground temperature .—Numerous observations in the mines lead to the 
conclusion that the average increment of underground temperature in the Cripple 
Creek district is about 1° F. for each 60 feet of depth. There is thus no special 
source of local heat that is likely to interfere with mining. As already mentioned, 
the mine gases have a temperature above that normal to the mines in which they 
occur. 


♦ 


GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE 
CREEK DISTRICT, COLORADO. 


By Waldemar Lindgren and Frederick Leslie Ransome. 


PART I-GENERAL DESCRIPTIONS, DISCUSSION, AND CONCLUSIONS. 

CHAPTER I—INTRODUCTION. 

FIELD WORK AND ACKNOWLEDGMENTS. 

The Cripple Creek gold deposits were discovered in 1891. Shortly afterwards, 
in 1894, an examination of the new district was undertaken by the United States 
Geological Survey, Mr. Whitman Cross having charge of geology and petrography 
and Mr. R. A. F. Penrose, jr., undertaking the examination of the mines. Their 
report, accompanied by a geological map, was published in the Sixteenth Annual 
Report of the Geological Survey, part 2, pages 1-207, and has for the last ten years 
served as a useful and accurate geological guide to mining operations. 

With the astonishingly rapid development of the Cripple Creek mines the 
opportunities for geological study multiplied. Great complexity of vein phenomena 
was thereby revealed and a desire arose for further investigation, particularly with 
reference to the question of the persistence of the veins in depth. This desire found 
expression in a request by citizens of Colorado for a reexamination of the district by 
the United States Geological Survey and in an offer of cooperation, whereby the 
cost would be equally divided between the State of Colorado and the national 
Survey. The total cost of the geological work was estimated at $7,000, and one-half 
of this amount, having been subscribed in Cripple Creek, Colorado Springs, and 
Denver, was put in the hands of Mr. John Wellington Finch, State geologist of 
Colorado, and by him disbursed as the State contribution. The cordial thanks of 
the geologists in charge of the work are due to Mr. Finch for his hearty and efficient 
cooperation. Of ,the State money, $780.22 was lost in a bank failure, but of this 
amount $300 was refunded by the Mine Owners’ Association. It proved necessary 
to make an additional allotment of $962.50 from the funds of the Geological Survey, 
so that the total expense for field work from June 20, 1903, to May 1 , 1904, amounted 
to $7,482.28, of which $3,019.78 was contributed by the State and $4,462.50 by the 
Geological Survey. The expenses of final office work, publication, and all topo¬ 
graphic work excepting the level line from Colorado Springs to Cripple Creek have 
been borne by the Geological Survey. 

The reexamination began with a thorough revision of the topographic map of 
Cripple Creek by Mr. R. T. Evans, Mr. E. M. Douglas in charge. This involved a 
great deal of painstaking work, nearly every prospect hole being located, as well as 
all shafts and tunnels. The new map is on the scale of 1:25,000, or about 24 inches 
to the mile, and includes practically the same area as the old map, a small strip only 

11 




12 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


being added on the western side, so that the total area mapped is about 40 square 
miles. The small developments outside of this area did not seem to justify further 
extension of the boundaries. Contours are 50 feet apart, and a numbered list of 324 
mines is given on the margin of the sheet. A line of accurate levels w r as run to 
Cripple Creek from Colorado Springs, thus settling the conflicting data of the differ¬ 
ent railroads. A bench mark was established at the National Hotel at Cripple 
Creek, in the south w r all of which an aluminum tablet is set. The height of this is 
derived from a point established by the Colorado Springs and Cripple Creek District 
Railroad, the top of a nail in a cross-tie in front of the station, the elevation of which, 



as corrected in accordance with the adjustment of 1903 by the United States Coast 
and Geodetic Survey at Colorado Springs, is accepted as 9,492.08 feet above mean 
sea level. Dependent on this the elevation of the datum tablet is accepted as 
9,495.136 feet above mean sea level. All permanent bench marks dependent on this 
datum are marked with the letters “CC” in addition to the figures of elevation. 
The datum plane commonly accepted before this accurate work was done, and used 
by Mr. V. G. Hills in his reports on the water conditions in the district, is 7 feet lower, 
so that to obtain the correct elevation 7 feet should be subtracted from his data. 
































FIELD WORK AND ACKNOWLEDGMENTS. 


13 


List of points in the Cripple Creek district determined by accurate levels. 

[N. S. Bright, levelman, under the direction of E. M. Douglas, geographer.] 

CIRCUITS IN CRIPPLE CREEK. 

Feet. 

Cripple Creek, opposite Midland Terminal station; top of rail. 9, 519. 8 

Cripple Creek, on southwest corner of City Hall; city bench mark. - .. 9,495. 551 

Cripple Creek, National Hotel, 3 feet west of south entrance, stone foundation; aluminum tablet, 

marked “9495 CC”. 9, 495. 136 

Cripple Creek, Teller County jail, in east end of stone doorsill, north entrance; aluminum tablet 

marked “9510 CC ”. 9, 509. 546 

CRIPPLE CREEK NORTHWEST AND NORTH, VIA RED MOUNTAIN UP SPRING CREEK, TO PIPE LINE; 
THENCE SOUTH, VIA HOOSIER PASS, VISTA GRANDE, WINDY POINT, ELKTON, AND ANACONDA, TO 
CRIPPLE CREEK. 

Feet. 

Cripple Creek, northwest corner of West Carr and C streets, 3 feet west of telegraph pole, on sand- 

rock outcrop; paint point... 9,553.81 

Cripple Creek, 1.5 miles northwest of, on saddle, northeast foot of Mount Pisgah, 40 feet north of 
road forks, near line of telegraph poles, in granite outcrop; aluminum tablet marked “9455 

CC’’ . 9,455.440 

Grand Review mine, 800 feet west of, 25 feet south of road, and 275 feet west of road forks; paint 

point on stone. 9,213. 606 

Standard tunnel, 0.25 mile south of, 10 feet north of road, 50 feet north of Spring Creek, in rock 

outcrop; aluminum tablet marked “9328 CC’’ . 9,327.928 

Standard tunnel, mouth of; top of east rail... 9, 524. 9 

Midway dairy, 120 feet north of road, in rock outcrop; aluminum tablet marked “9817 C C ”. 9,816. 810 

Midway dairy, 1 mile east of, 1 mile south of Lincoln mine, 50 feet east of pipe line, in triangle of 

roads; iron post marked “ 10088 C C”.. 10,087.711 

Tenderfoot Consol, southeast corner of gallows frame; nail in top of mudsill... 10, 420. 67 

The Friday, northeast corner of gallows frame; spike in collar... 10, 401. 25 

Hoosier, northeast corner of gallows frame; nail.,.. 10, 378. 98 

Hoosier Pass, between main line Colorado Springs and Cripple Creek District Railway and switch, 

12 feet west of public road, between two posts supporting Hoosier Pass signboard; iron post 

marked “ 10315 CC’’ . 10,314.743 

Iron Clad, southeast corner of engineer room; nail in top of timber. 10, 401. 36 

Vista Grande, or Midway station, 13 feet west of Florence and Cripple Creek Railroad track, 1 foot 

south of signpost “ Vista Grande;’’ iron post marked “10487 C C ”. 10, 486. 749 

Windy Point, upper road crossing; top of south rail. 10, 444. 6 

War Eagle mine, southwest corner of gallows frame; nail.*. 10,355. 91 

Bull Hill, west mudsill gallows frame; nail. 10,029, 98 

Elkton, Elkton Consolidated Mining and Milling Company, in stone foundation, south corner of. 

south stack; alumirgun tablet marked “9734 C C”. 9,733. 753 

Anaconda, 400 feet south of Midland Terminal Railroad depot, 6 feet east of track, in wall of rock 

cut; aluminum tablet marked “9525 C C”. 6, 524. 816 

Anaconda, 1 mile northwest of, 450 feet north of Worlds Fair, 8 feet west of Midland Terminal 

Railroad track, in granite outcrop; aluminum tablet marked “9534 CC”. 9, 534. 034 

HEAD OF SPRING CREEK, VIA GILLETT, VICTOR PASS, AND GOLDFIELD, TO ELKTON. 

Midway dairy, 1 mile east of, west side of divide and Cripple Creek road, on northeast side of curb¬ 
ing to Cripple Creek pipe line; nail in top. 10,084. 685 

Gillett, 1.25 miles east of, 100 feet south of road forks, claim 14888; nail in top of post 3. 10 049. 66 

Lincoln, east side of gallows frame; nail.:.-.- - - 10,068. 81 

Gillett, 1.25 miles west of, 600 feet south of Lincoln mine, 20 feet west of road forks, in phonolite- 

rock outcrop; aluminum tablet marked “ 10021 C C ’... 10,021.130 

Gillett, in stone foundation of unfinished electric-light plant, in west wall 1 foot north of southwest 

corner; aluminum tablet marked “9940 C C ... 9.939 742 

13001—No. 54—06-3 






























14 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


. Feet. 

Gillett, in front of Midland Terminal Railroad station: top of rail. 9, 934. 3 

Gillett, 1.5 miles south of, 60 feet east of track; chiseled cross. 9,877. 40 

Gillett, 2.5 miles south of, 1,000 feet south of milepost 17, in granite wall 8 feet west of Midland 

Terminal Railroad track; aluminum tablet marked “9841 C C”. 9, 840. 752 

Milepost 18, 750 feet west of, at road crossing, 10 feet north of track; railroad spike in signpost 

(north side). 9,878.06 

Cripple Creek sampler, 0.5 mile north of, 20 feet west of road; cross cut in flat rock. 10,123. 26 

Cripple Creek Sampler and Ore Company, 425 feet east of, in Victor Pass, 12 feet south of Midland 

Terminal Railroad track, 1 foot east of telephone pole; iron post marked “ 10202 CC”. 10,201. 976 

Goldfield, north side of Ninth street, between Main and Portland, entrance to Red Mens Hall, in 

west end of stone doorsill; aluminum tablet marked “9903 C C”. 9,903. 197 

Goldfield, in front of Florence and Cripple Creek Railroad station (line continued along railroad).. 9,882. 8 

Stratton Junction; top of railroad frog. 9,809.1 

Victor, in front of Colorado Springs and Cripple Creek District Railway station; top of rail. 9,707. 7 

Victor, Colorado Trading and Trust Company Building, northeast corner Diamond avenue and 

Third street, in north end stone doorsill : bronze tablet marked “9718 C C”. 9, 717. 748 

Victor, in front of Florence and Cripple Creek Railroad station; top of rail. 9, 729. 4 

Victor, in front of Midland Terminal Railroad station; top of rail. 9,7?1. 8 

Victor, 0.9 mile northwest of, 100 feet north of switch back, east side of track; spike in telegraph 

pole. 9,842. 61 


ANACONDA, WORLD’S FAIR MINE NO. 50, SOUTHWEST DOWN CRIPPLE CREEK ALONG THIRD-CLASS 
ROAD; THENCE WEST TO PONY GULCH; THENCE NORTH-NORTHEAST TO CRIPPLE CREEK. 


Feet. 

Ophelia tunnel, west entrance : top of north rail. 9,268. 9 

Mound, 0.5 mile southwest of, west side of Cripple Creek, 200 feet south of road, in granite out¬ 
crop; aluminum tablet marked “ 9232 C C ”. 9,231.837 

Field’s ranch, 0.75 mile southwest of, 200 feet east of road forks, on saddle, south side of Deadox 

Gulch, in granite outcrop; aluminum tablet marked “9133 C C”. 9,132. 604 

G. P. Taft’s cabin, 100 feet west of; nail in top of 20-inch pine stump.. 9,074. 88 

Arlington dairy, 2,000 feet north of, west side of Pony Gulch, east side of road, in granite outcrop; 

aluminum tablet marked “9113 C C”. 9,112. 852 

Cripple Creek, 1.25 miles south of, 700 feet north of powder magazines, in road forks, set in granite 

outcrop; bronze tablet marked “ 9393 C C ”. 9,392.874 


The geological and mining work was undertaken jointly by the authors of this 
report. Mr. L. C. Graton served as assistant throughout, participating most 
efficiently in all branches of the work. Messrs. A. M. Rock and J. Bruce also ren¬ 
dered excellent aid as draftsmen. Air. Lindgren undertook the preliminary exami¬ 
nation from June 24 to July 12, 1903, and finished the mining work during the three 
months from February 1 to May 1, 1904. Mr. Ransome took the field from July 4 
to August 4 and from August 19 to October 10, 1903; also from January 7 to Feb¬ 
ruary 2, 1904. In a general way the mines of the southwestern part of the area 
shown in the detailed map have been examined and described by Mr. Ransome.and 
those of the northeastern part by Mr. Lindgren, but each of the authors has 
visited all the important mines in the district. A number of smaller mines have 
been described by Mr. Graton. The work of areal mapping was undertaken by Mr. 
Ransome, with the aid of Mr. Graton. • 

To all the mine owners, managers, engineers, and other gentlemen interested 
in the mining industry our sincere thanks are due for their cordial cooperation. 
They have aided us by their experience and allowed us without reserve to inspect 
their mines, to examine their maps, and to ascertain their output, and this friendly 





















LITERATURE. 


15 


attitude has more than anything else assisted our work. Particularly do we desire 
to express our appreciation of the many courtesies extended to us by the mining 
engineers of the district, including Messrs. Countryman & Jaquith, Hills & Willis, 
Haff & Colwell, Charles J. Moore, and James Smith, of Cripple Creek; and Messrs. 
Davis & Byler and Bodfish & Atherton, of Victor. To the excellent professional 
work of all these and to their hearty personal cooperation we are deeply indebted. 
The chemical division of the Geological Survey has aided us by many detailed and 
careful analyses, made by Messrs. W. F. Hillebrand, George Steiger, and W. T. 
Schaller. 

LITERATURE. 

The following list is intended to include the important publications on the Crip¬ 
ple Creek district, particularly those having some geological or historical signifi¬ 
cance. Articles of less value are scattered through mining journals, and consider¬ 
able information is sometimes obtainable from special mining editions of the local 
newspapers and from the published annual reports of a few of the larger companies, 
such as the Portland and Stratton’s Independence. 

LIST OF PUBLICATIONS ON THE CRIPPLE CREEK DISTRICT. 

Bancroft, George J. Secondary enrichment at Cripple Creek. Engineering and Mining Journal, vol. 74, 
1902, pp. 752-753. 

Suggests that below the zone now worked in the Cripple Creek district there may be a zone of second¬ 
arily enriched ores. It is thought that the occurrence of tetrahedrite in the lower levels of some of the 
mines is indicative of such deep enrichment. This article was followed by a discussion in succeeding 
numbers of the journal. 

Bancroft, George J. The bottom levels at Cripple Creek, Colorado. Engineering and Mining Journal, vol. 
^6, 1903, pp. 86-88. 

A review of conditions at the bottoms of some of the deeper mines, with particular reference to 
drainage and to enrichment or impoverishment of the ore. 

Blake, William P. The gold of Cripple Creek. Engineering and Mining Journal, vol. 57, 1894, p. 30. 

Suggests that the “sylvanite” is probably for the most part calaverite or krennerite. 

Cross, Whitman. Geology of the Cripple Creek gold mining district, Colorado. Colorado Scientific Society, 
Proceedings, vol. 5, 1894-1896, pp. 24-49. 

A preliminary outline, based on field work in 1893 on the Pikes Peak quadrangle. 

Cross, W., and Penrose, R. A. F., jr. The Pikes Peak folio. Geologic Atlas of the United States, folio 7, 
U. S. Geol. Survey, 1894. 

Contains a detailed geological map of the Cripple Creek district and brief descriptions of the geology 
and ore deposits. 

Cross, W., and Penrose, R. A. F., jr. The geology and mining industries of the Cripple Creek district, Colo¬ 
rado. Sixteenth Ann. Rept. U. S. Geol. Survey, pt. 2, 1895, pp. 1-209. 

The best and most complete account of the geology and ore deposits of Cripple Creek. 

Curle, J. H. The gold mines of the world. Second edition, London, 1902, pp. 271-284. 

. Particularly valuable as a shrewd and unprejudiced review of the mines from the financial standpoint. 
Finch, John W. The circulation of underground aqueous solutions and the deposition of lode ores. Colorado 
Scientific Society, Proceedings, vol. 7, 1904, pp. 193-252. 

A paper treating of ore deposition in general, but with special application to Cripple Creek, whence 
most of the illustrations are drawn. 

Hillebrand, W. F. Calaverite from Cripple Creek, Colorado. American Journal of Science, 3d ser., vol. 50, 
1895, pp. 128-131. 

Shows by chemical analyses that specimens from the Prince Albert, Raven, and C. O. D. mines have the 
composition of calaverite. Crystallographic study by Penfield indicates that the crystals are probably 
triclinic, but are near sylvanite in angles and axial ratios. 




16 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


Hills, Fred. The official manual of the Cripple Creek district, vol. 1. Colorado Springs, 1900. 

A useful compilation giving the organization, holdings, and equipment of each mining company in the 
district. 

Hills, Victor G. Water record of mines at Cripple Creek, Colorado. Engineering and Mining Journal, vol. 
76, 1903, p. 117. 

A record of 39 mines in tabular form. 

Hills, Victor G. Water in the mines of Cripple Creek. Engineering and Mining Journal, vol. 76, 1903, 
pp. 19.5-197. 

Concludes from the study of carefully collected data that, from a practical standpoint, the mines do not 
have a common water level, and that pumping in one mine does not necessarily lower the water in a 
neighboring mine. 

Knight, F. C. A suspected new mineral from Cripple Creek. Colorado Scientific Society, Proceedings, vol. 
5, 1894-1896, pp. 66-71. 

Concludes from chemical studies that in the oxidation of calaverite a part of the tellurium may combine 
with iron to form a tellurite. 

Liebenam, W. A. Der Cripple Creek Golddistrikt, seine Entdeckung, Entwicklung, Geologie und Zukunft. 
Berg- und huttenmannische Zeitung, vol. 63, 1904, pp. 2-5, 29-32, 57-60, 89-92, 117-121, 161-164. 

An extended account of the district, for the most part a compilation, with rather slight acknowledg¬ 
ment, from writings of Cross, Penrose, and Rickard. 

Lindgren, W. Metasomatic processes in fissure veins. Transactions American Institute of Mining Engineers, 
vol. 30, 1901, pp. 612, 630-631, 654-657. 

The first recognition of adularia (valencianite) as a vein mineral at Cripple Creek. 

Lindgren, W., and Ransome, F. L. Report of progress in the geological resurvey of the Cripple Creek district, 
Colorado. Bull. U. S. Geol. Survey No. 254, 1904. 

A brief preliminary statement of results. 

Mathews, E. B. The granites of Pikes Peak, Colorado. Geological Society of America* Bulletin, vol. 6, 
1895, pp. 471-473. 

A petrographical study of the granitic rocks of the Cripple Creek region. 

Mathews, E. B. The granitic rocks of the Pikes Peak quadrangle. Journal of Geology, vol. 8, 1900, pp. 
214-240. 

A detailed petrological study of the granites of the Cripple Creek region. Four types are distinguished, 
three of which are recognized as occurring in the Cripple Creek district. 

Myers, W. S. Quoted in “On krennerite from Cripple Creek, Colorado,” by Albert H. Chester. American 
Journal of Science, 4th ser., vol. 5, 1898, pp. 375-377. 

A chemical analysis of material from the Independence mine. 

Palaciie, Charles. Notes on tellurides from Colorado. American Journal of Science, 4th ser., vol. 10, 1900, 
pp. 419-427. Also a German translation in Zeitschrift fur Krystallographie und Mineralogie, vol. 34, 
1901. 

Chemical and crystallographic study of crystals from two localities in the Cripple Creek district proves 
them to be sylvanite. It is shown that the supposed new mineral goldschmidtite is really sylvanite. 

Pearce, Richard. The mode of occurrence of gold in the ores of the Cripple Creek district. Colorado Scien¬ 
tific Society, Proceedings, vol. 5, 1894-1896, pp. 5-10. 

Shows that the gold, prior to oxidation, occurs as a telluride, probably as sylvanite. Tests of various 
samples of oxidized ore indicate that oxidation, while setting free the gold, increases the ratio of 
tellurium to gold in the ore. 

Pearce, Richard. The occurrence of gold in the ores of the Cripple Creek district. Engineering and Mining 
Journal, vol. 57, 1894, p. 271. (Abstract of a paper read before the Colorado Scientific Society.) 

Shows that the usual ratio of gold to silver in the Cripple Creek ores corresponds to the composition of 
sylvanite rather than to that of krennerite or calaverite. 

Pearce, Richard. Further notes on Cripple Creek-ores. Colorado Scientific Society, Proceedings, vol. 5, 
1894-1896, pp. 11-16. 

Points out that tellurium, in oxidized form, is always present with gold in the oxidized ore, and usually 
in much greater proportion than in the unoxidized ore. It is concluded that part of the gold and most 
of the silver originally present in the sylvanite is removed in solution during oxidation. 


LITERATURE. 


17 


Penfield, S. L. Quoted in “On krennerite from Cripple Creek, Colorado,” by Albert II. Chester. American 
Journal of Science, 4th ser., vol. 5, 1898, pp. 375-377. 

A crystallographic study of a specimen from the Independence mine. 

Penfield, S. L., and Ford, W. E. On calaverite. American Journal of Science, 4th ser., vol. 12, 1901, pp. 
225-246. Also a German translation in Zeitschrift fur Krystallographie und Mineralogie, vol. 35, 1902, 
pp. 430-451. 

The authors conclude that the apparent monoclinic symmetry is the true symmetry of the mineral, 
notwithstanding the extraordinarily complex crystallographic symbols which that supposition demands. 

Penrose, R. A. F., jr. The ore deposits of Cripple Creek, Colorado. Colorado Scientific Society, Proceedings, 
vol. 5, 1894-1896, pp. 50-53. 

A preliminary outline, written before detailed examination of the district had begun. 

Penrose, R. A. F., jr. [-See also under Cross and Penrose.] 

Rickard, T. A. The Cripple Creek gold field. Institution of Mining and Metallurgy (London), Transactions, 
vol. 8, 1899-1900, p. 49-111. 

Contains an interesting account of the early history of the district, an outline of the general geology, a 
description of the ore deposits, statistics of production, and notes on the mines. 

Rickard, T. A. The telluride ores of Cripple Creek and Kalgoorlie. Engineering and Mining Journal, vol. 
70, 1900, p. 611. 

Gives an interesting account of the Cripple Creek ores from mineralogical, chemical, and metallurgical 
standpoints. 

Rickard, T. A. The Cripple Creek volcano. Transactions American Institute of Mining Engineers, vol. 30, 
1901, pp. 367-403. 

A semipopular summary of the geological history of the district. 

Rickard, T. A. The lodes of Cripple Creek. Transactions American Institute of Mining Engineers, vol. 33, 
1903, pp. 578-618. 

Describes in considerable detail, with numerous illustrations, the structural characteristics of the lodes. 

Schwarz, T. E. The Independence mine, Cripple Creek, Colorado. Colorado Scientific Society, Proceedings, 
vol. 4, 1893, p. 422. 

Describes the essential geological features of the Independence vein as exposed at that time. 

Skewes, E. The ore shoots of Cripple Creek. Transactions American Institute of Mining Engineers, vol. 26, 
1896, pp. 553-579. 

Records some facts of interest relative to the upper portions of the ore bodies of the Elkton, Raven, 
and Doctor mines. 

Smith, G. F. Herbert, and Prior, G. T. On the remarkable problem presented by the crystalline develop¬ 
ment of calaverite. Mineralogical Magazine, vol. 13, 1901-1903, pp. 122-150. 

The authors conclude that the mineral is either monoclinic with remarkably complex symbols, or tri¬ 
clinic with extraordinary complicated twinning. 

Stevens, E. A. An occurrence of limburgite in the Cripple Creek district. Transactions American Institute 
of Mining Engineers, vol. 30, 1901, pp. 759-764. 

Describes the occurrence of a dike at the western edge of the town of Victor. 

Stevens, E. A. Basaltic zones as guides to ore deposits in the Cripple Creek district, Colorado. Transactions 
American Institute of Mining Engineers, vol. 33, 1903, pp. 686-698. 

Maintains that there is a genetic relation between the basaltic dikes and ore deposition and that the 
type of rock is more important than the structure in determining the occurrence of ore. 

Stone, G. II. The granitic breccia of the Cripple Creek region. American Journal of Science, 4th ser., vol. 5, 
1898, pp. 21-32. 

An atterppt to explain several deposits of diverse origin as breccias produced by the shattering of the 
older rocks by igneous intrusions. 

Van Hise, C. R. A treatise on metamorphism. Mon. U. S. Geol. Survey, vol. 47,1904, pp. 1120-1125, and 
elsewhere. 

Discusses Cripple Creek deposits in connection with a general treatment of the problems of ore genesis. 
The rich telluride ores are regarded as secondary concentrations due to descending waters. 


I 


CHAPTER II.—GENERAL GEOLOGY. 


INTRODUCTORY STATEMENT. 

In view of the well-known work of Mr. Cross, it is not necessary,' as in the 
earlier report, to present a detailed account of the geology of the district. The 
general relations of the rocks and the main facts of the volcanic historj" are now 
familiar to those interested in the region, and the first official report is still a 
valuable source of detailed and accurate descriptions of particular localities. The 
plan adopted in the present work, therefore, does not contemplate so exhaustive 
a description of the district as would be appropriate in a new geological field. It 
is proposed to recount briefly the essential results obtained by Mr. Cross and to 
indicate in a few words the general character of the modification of these results 
required by later study. Mr. Graton’s report on the petrography of the Cripple 
Creek rocks, presenting further details of the changes involved, forms a separate 
chapter and is followed by a sketch of the geological structure of the district with 
such additional matter as is necessary to supply a satisfactory geological basis 
for the discussion of the ore deposits. 

The new geological map of the district forms PI. II and is accompanied by 
five sections, on which full black lines indicate that the contact lines are actually 
known from mining developments. 

FIRST GEOLOGICAL SURVEY OF THE OISTRICT. 

When Mr. Cross made his careful study of the geology of the Cripple Creek 
district ten years ago, mining had barely begun and the various hills were not, 
as now, perforated by deep underground workings. That his work has in general 
stood the test of subsequent mining exploration and continues to be highly regarded 
in the district is convincing testimony to its excellence. Later workers, however 
they may amplify or modify his results, should fairly acknowledge their debt to 
the pioneer who first unraveled the structure and deciphered the historj' of the 
Cripple Creek volcanic complex. The account of the district as given by Cross 
may be very briefly summarized as follows: 

The Cripple Creek hills lie near the eastern border of a lofty and deeply dis¬ 
sected plateau which slopes gently westward for 40 miles, from the southern end 
of the Colorado Range, dominated by Pikes Peak, to the relatively low hills con¬ 
necting the Mosquito and Sangre de Cristo ranges. The prevailing rocks of this 
plateau are granites, gneisses, and schists. The granites inclose masses of Algonkian 
quartzite and are therefore post-Archean, but they are older than the only Cambrian 
sediments known in Colorado. During Tertiary time volcanic eruptions broke 
through these ancient rocks at several points and piled tuffs, breccias, and lavas 


18 


U. S. GEOLOGICAL SURVEY 


PROFESSIONAL PAPER NO. 54 PL. IV 



A. CRIPPLE CREEK. LOOKING WEST FROM GOLD HILL. 

The Midget and Conundrum mines are in the foreground and Mount Pisgah is in the background. 



The partly wooded knob on the left is Rhyolite Mountain. Just beyond the town are Mineral and Carbonate hills, and in the background is 

Pikes Peak. 
























































GENERAL GEOLOGY. 19 

upon the uneven surface of the plateau. The eruptive rocks of the Cripple Creek 
district are the products of one of the smaller isolated volcanic centers of this 
period, a center characterized by the eruption of phonolite, which does not occur 
elsewhere in this general region. The most voluminous products of the Cripple 
Creek volcano now preserved are tuffs and breccias. They occupy a rudely ellip¬ 
tical area in the center of the district about 5 miles long in a northwest-southeast 
direction and about 3 miles wide. According to Cross, these breccias and tuffs 
rest in part upon an earlier flow of andesite," but mainly upon an unevenly eroded 
surface of the granites and schists, although along the southwest edge of the area 
the contact was found to be so steep as "to support the idea that the central vent 
or vents of the volcano were adjacent to this line.” The breccia is much indurated 
and altered, but was thought to consist mainly of andesitic fragments, although 
it was recognized that fragments of phonolite are locally abundant. The most 
characteristic massive rock emanating from the Cripple Creek volcano is phonolite, 
which was erupted at several periods and more abundantly than any other type. 
It occurs as dikes and masses, not only in the breccia, but in the surrounding granitic 
rocks. Among the massive rocks distinctly younger than most of the breccia 
Cross distinguished trachytic phonolite, nepheline syenite, syenite porphyry, mica 
andesite, pyroxene andesite, and basaltic rocks of various types. The nepheline 
syenite he considered as probably younger than the trachytic phonolite, while the 
basaltic dikes represent the last eruptions in the district. 

MODIFICATION OF EARLIER 1IFST FTS. 

In the course of the present investigation the geology of the district has been 
entirely remapped upon the carefully revised topographic base. A comparison 
of the new map with the old will reveal a number of changes in the boundaries of 
igneous masses, the division of the granitic terrane into several distinct formations, 
the recognition of a number of eruptive masses not shown on the older map, and 
considerable change in the nomenclature of the igneous rocks. There is also 
recorded an important revision of conclusions as to the age and the relation to the 
rhyolite of the sedimentary rocks of Grouse Hill and Straub Mountain. 

BASEMENT ROCKS. 

The most ancient rocks in the district are fibrolitic muscovite schists and fine¬ 
grained granitic gneisses. The gneisses are typically exposed in the streets of 
Cripple Creek and at the terminal station of the Colorado Springs and Cripple 
Creek District Railway. The schists may be well seen in Poverty Gulch between 
the Abe Lincoln mine and the railway trestle bridge and near the station of the 
Florence and Cripple Creek Railroad in Cripple Creek. This gneiss v^as not separa tely 
shown on the older map, being included partly with the granites, which were mapped 
as a unit, and partly with the schist. 

Cross and Mathews recognized three types of granite in the Cripple Creek 
region, which they designated the Pikes Peak, Cripple Creek, and Spring Creek 
types. They did not, however, distinguish these types upon the map. This has 

a At the time Cross wrote, the term “andesite” embraced rocks, such as latite, which have since been given separate 


names. 



* 

20 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

now been done. The Pikes Peak granite prevails over a large area in the district 
and is the common rock in the vicinity of Squaw Mountain and Victor. It is 
younger than the gneiss and schist. The Cripple Creek granite also occupies a 
considerable area extending westward from Anaconda beyond the bounds of the 
area studied and is well exposed along Cripple Creek in the vicinity of Mound. It 
cuts the schist and gneiss and is intrusive into the Pikes Peak granite. The Spring 
Creek granitic mass is of comparatively small superficial extent, and its age with 
reference to the other granites is unknown. 

In the northwestern part of the district there has been found and mapped an 
area of a rock which is mainly an olivine syenite, though the mass exhibits remark¬ 
able range and variability in mineralogical composition. The olivine syenite is 
younger than the Pikes Peak granite, but is pre-Tertiary, for numerous diabase dikes 
genetically related to the syenite are covered or intruded by Tertiary eruptive 
rocks. A dike of anorthosite cuts the olivine syenite and is genetically related 
to it in a manner similar to pegmatite dikes in granite. 

It will be seen on looking at the map that the schist, gneiss, Spring Creek 
granite, Cripple Creek granite, and olivine syenite together constitute a wedge- 
shaped area projecting into the Pikes Peak granite from the west. The center 
of volcanic disturbance is near the point of this wedge. 

VOLCANIC ROCKS. 

A number of new chemical analyses of the Tertiary eruptive rocks have been 
made by Dr. W. F. Hillebrand, Mr. George Steiger, and Dr. W. T. Schaller for this 
report, and the petrography of the district has been carefully studied by Mr. L. C. 
Graton with interesting results. That the phonolite, nepheline syenite, trachytic 
phonolite, syenite porphyry, and andesite of Cross are all closely related types 
connected by intermediate varieties appeared highly probable in an early stage of 
the field work. Mr. Graton’s studies, in connection with the chemical analyses, 
confirm this view and show clearly that all the volcanic rocks, including the -basic 
dikes, are merely divergent eruptive facies of one general magma, characterized 
chemically by about 58 per cent silica, a large proportion of alkalies, the soda being 
usually somewhat higher than the potash, a small percentage of lime and magnesia, 
and a certain quantity of combined water. None of the massive rocks would now be 
called andesite. Though it can not be affirmed that andesitic fragments are entirely 
absent from the usually much altered volcanic breccia, none were recognized and 
the term “andesitic breccia” is certainly not applicable to this formation as a 
whole. It would be more accurate to describe it as a phonolitic breccia, although 
in places near the periphery it consists chiefly of particles of the older rocks through 
which the Tertiary eruptives broke. 

None of the massive rocks erupted from the Cripple Creek volcanic center 
and now present in the district show any evidence of having been surface flows. 
They are for the most part intrusive porphyries, ranging in texture, however, from 
the granular so-called nepheline syenite near Independence to the nearly aphanitic 
phonolite of the smaller dikes and sheets. In the breccia of Rhyolite" Mountain, 
however, and in a smaller area of breccia at the south boundary of the district 
mapped, on the east side of the canyon of Cripple Creek, some of the breccia frag¬ 
ments are vesicular. 


GENERAL GEOLOGY. 


21 


Much difficulty was experienced during the mapping in an attempt to separate 
the rocks described and mapped by Cross as trachytic phonolite, syenite por¬ 
phyry, pyroxene andesite, and augite-mica andesite. The more carefully their 
occurrences were studied, particularly in underground exposures, the more apparent 
it became that these rocks are not distinct, but are slight variants of one magma 
and, in some places, of one eruptive mass. New chemical analyses and the latest 
petrographic work show that this view is correct. The names “ trachytic phonolite,” 
“syenite porphyry,” “pyroxene andesite,” and “augite-mica andesite” have 
accordingly been dropped and the corresponding rocks have been designated “latite- 
phonolite.” Although some of the augite-mica andesite of Cross is sufficiently 
distinct to be called “biotite trachyte,” it has not seemed advisable to map this 
facies as a separate unit. 

On the older map is shown an area of nepheline syenite near the town of Inde¬ 
pendence. Some important changes have been made in the geological boundaries 
in this part of the field, and the rock originally called “nepheline syenite” is in the 
present report described as syenite. A small area of similar rock has also been 
mapped on the north side of Battle Mountain. Nepheline, if present at all in these 
rocks, is a very subordinate constituent. 

The syenite areas are difficult to map, as the rock in many places passes through 
imperceptible gradations into latite-phonolite. 

Cross, in the first Cripple Creek report , a described the rock forming the sum¬ 
mit of Bull Cliff and called attention to its peculiar character. It was mapped by 
him as phonolite. but he stated that it was widely different from the other phono- 
lites and might be a distinct intrusion. Field examination in 1903 showed the rock 
to be a sheet capping the hill and resting upon breccia and latite-phonolite. In the 
Pilgrim tunnel, on the west side of Bull Cliff, the fact that this capping rock is 
younger than a dike of latite-phonolite is clearly shown. 

We classify this rock as a trachydolerite. It apparently constitutes an inter¬ 
esting link, both in time and in chemical composition, between the phonolitic 
rocks and the basic dikes which were the final eruptive products from the Cripple 
Creek volcanic center. 

FORM OF THE VOLCANIC NECK. 


While it may be true that in a few places the breccia rests upon an uneven 
erosion surface of granite, gneiss, and schist, the evidence obtained during the season 
of 1903 shows that the main breccia mass fills a steep-walled chasm of profound 
depth in the fundamental rocks of the region. From the Conundrum mine, on 
the western slope Gold Hill, to Stratton’s Independence mine, on the south slope 
of Battle Mountain, the contact plunges steeply down, with dips ranging in general 
from 70° to vertical. In some places the granite walls of this chasm actually 
overhang the breccia. It is certain that this entire southwest contact represents 
a part of the wall of the great pit formed by the volcanic explosions that produced 
the breccia. In most of the other parts of the contact where evidence could be 
obtained the walls are also steep. The general conclusion reached is that the 
principal breccia mass, with its associated bodies of intrusive rocks, is in the main 
a volcanic neck. 


a Sixteenth Ann. Rept. U. S. Geol. Survey, pt. 2, 1895, p. 37. 




22 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

f > 

SEDIMENTARY DEPOSITS. 

The hill occupied by the city reservoir on the northern edge of Cripple Creek 
is capped by a coarse conglomerate containing rounded bowlders of granite, gneiss, 
schist, and diabase up to a foot or more in diameter. Pebbles derived from the 
Tertiary eruptive rocks appear to be entirely absent. The bowlders are weathered 
and decomposed, and the deposit at its north end seems to underlie the volcanic 
breccia of Mineral Hill. 

This conglomerate was mapped as breccia by Cross, as the exposures available 
for his examination indicated the presence of some volcanic material. He showed, 
however, ° that the general material of the deposit was entirely different from the 
normal breccia and suggested that it was probably a remnant of a local lake 
deposit. The character of the conglomerate, which since Mr. Cross’s visit has been 
well exposed in a street cuttin'g, indicates that it is a stream deposit. The occur¬ 
rence is of particular interest because it affords definite information concerning the 
original character of the surface of the region before the eruptions of the Cripple 
Creek volcano commenced. 

On Grouse Hill and Straub Mountain occur some rather obscurely bedded 
grits which are remnants of a formerly more extensive deposit. The material con¬ 
sists chiefly of angular and rounded particles of granite, occasionally several cen¬ 
timeters in diameter. Quartz pebbles are abundant and there are scattered pebbles 
of a hard bluish quartzite. The usual color of these grits ranges from dark brown 
to brilliant red or yellow. 

In describing these sediments Cross b referred to their great similarity to the 
upper Carboniferous grits of the Fountain formation. Believing, however, that 
they rested as a younger formation upon the rhyolite of Grouse Hill and Straub 
Mountain, he correlated them with the Miocene High Park lake beds, and deduced 
partly from this correlation the probable late Miocene age of the Cripple Creek 
volcano. 

The relation between the rhyolite and these grits has been studied by Mr. 
Graton, who finds that the rhyolite is intrusive into the grits and the latter are thus 
older than the High Park lake beds. Fragments of rhyolite, it is true, occur in the 
grits near the intrusive contact, but these were probably introduced at the time of 
intrusion of the eruptive rock into the loose, porous deposit. 

The origin and correlation of these grits, including a small mass of similar 
material found on Copper Mountain, in the northern part of the district, is doubtful. 
It is possible that they are remnants of the Fountain formation. But it seems more 
likely that, as suggested by Cross, they are composed of detritus blown from the 
throat of the Cripple Creek volcano at an early stage of eruptive activity, and that 
they have been protected from erosion by the induration consequent on the intrusions 
of rhyolite and phonolite and by cappings of phonolite. 

The deposit seems to have been at least from 200 to 300 feet thick in the vicinity 
of Grouse Hill and Straub Mountain. The accumulation of this thickness of material 
upon what appears to have been in general a plateau surface is difficult to reconcile 
with the supposition that the grits were deposited in a lake. It is more probable 


a Sixteenth Ann. Rept. U. S. Geol. Survey, pt. 2, 1895, p. 101. 


b Op. cit., pp. 53-55, 106-109. 






GEOLOGICAL STRUCTURE OF THE DISTRICT. 


23 


that the material was thrown into the air by an explosive eruption and fell thickly 
upon the surrounding plateau, to be in some places partially reworked and distrib¬ 
uted by streams. 

AGE OF THE ERUPTIONS. 

The fact that the grits of Grouse Hill and Straub Mountain can not be correlated 
with the High Park lake beds does not involve any great change in the assignment 
of a probable geological date to the Cripple Creek eruptions. Inasmuch as the 
accumulation of the grits probabty marked the beginning of local volcanic activity, 
and as both grits and rhyolite are intruded by phonolite from the Cripple Creek 
center, it follows that the Miocene (or at least post-Oligocene) rhyolite was erupted 
within the period during which the Cripple Creek volcano was active. 

GEOLOGICAL STRUCTURE OF TIIE DISTRICT. 

CRYSTALLINE ROCKS OF THE PREVOLCANIC PLATEAU. 

As appears from the accompanying map (PI. II), the schist and gneiss occur 
chiefly in the northwest corner of the district. The two rocks are in irregular and 
intimate association and constitute a thoroughly metamorphosed complex of 
unknown derivation. It is probable, however, that the gneiss was originally a 
granitic rock and there is some evidence to support the view that the schist, which 
at the present time is composed of muscovite, quartz, fibrolite, and magnetite, is 
an extremely metamorphosed sediment. The two rocks exhibit intermediate facies 
and can not everywhere be distinguished. This metamorphism was probably 
effected in pre-Cambrian time and long antedates the eruptions from the Cripple 
Creek volcanic center. 

The olivine syenite and Spring Creek granite occur in the extreme northwest 
corner of the district and are intrusive in the gneiss and schist. 

The Pikes Peak granite is the most extensively developed formation in the 
district. It is prevalent on the north, east, and south sides of the central volcanic 
area and is the principal rock of the plateau country for miles in these directions. 
It is intrusive into the gneiss and schist, and probably also into the Spring Creek 
granite and the olivine syenite. 

The Cripple Creek granite occupies a considerable area in the western part of t-he 
district, west and southwest of the town of Cripple Creek. It is clearly intrusive 
into the gneiss and schist and has invaded these rocks irregularly, not only in large 
masses, but in numerous dikes, as may be well seen at many points in the southern 
part of Cripple Creek town. The reddish color of the younger rock, contrasting 
with the gray tint of the gneiss and schist, renders these dikes readily recognizable. 
It is probably intrusive also into the Pikes Peak granite; for though no decisive 
evidence bearing upon this point was found within the district, yet the occurrence 
in the Pikes Peak granite of fine-grained granitic dikes which are similar in litho¬ 
logical character to the Cripple Creek granite, the absence of gneissic structure in 
the latter and its frequency in the Pikes Peak granite, particularly near the contact 
of the two rocks, are indicative of this relation. Shear zones, along which the 
sheared granite is often metamorphosed to schist, occur in the Pikes Peak granite, 
but not, so far as observed, in the Cripple Creek granite. Such schist bands are 


24 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

f 

particularly abundant in the vicinity of the contact between the two granites south¬ 
west of Guyot Hill. Cross and Mathews, from their studies in the Pikes Peak 
quadrangle, reached the same conclusion with regard to the relative age of these 
granites. 

Before the Tertiary eruptions broke through the plateau the principal mass of 
Cripple Creek granite probably extended eastward to West Beaver Creek, for the 
granite between Bull and Ironclad liills and some masses near Cameron are of this 
type. In the southern part of the district, near Victor, are some small bodies of 
similar granite apparently intrusive in the Pikes Peak granite. 

The various intrusive contacts between the pre-Cambrian rocks are unaccom¬ 
panied by any important mineralization, even pvrite being notably lacking in these 
rocks, and the prevolcanic structure of the ancient crystalline plateau is of economic 
importance only in so far as it affects the distribution of the different rock types in 
the rim of the volcanic conduit . Practical^ no deposits of value occur, for example, 
in schist, but some of the most productive ore bodies in the district have been found 
in the Pikes Peak granite close to the irruptive contact. The Cripple Creek granite, 
moreover, where it forms a part of the rim has proved less productive than the 
gneiss. It is thus probable that the economic history of the district would have 
been different had not the prevolcanic structure determined that a large part of the 
volcanic neck, particularly between Guyot Hill and Goldfield, should be bordered 
by the Pikes Peak granite. It has already been pointed out that the principal 
volcanic eruptions broke through the pre-Cambrian rocks near the point of a wedge¬ 
like projection of gneiss, schist, Cripple Creek granite, Spring Creek granite, and 
olivine syenite into the Pikes Peak granite. It is possible that this was not a mere 
coincidence, but that the pre-Cambrian structure as revealed in this areal distri¬ 
bution of the rocks was an important factor in determining the point of eruption. 

The granites and gneiss of the Cripple Creek district are cut by a number of 
diabase dikes that are older than the Tertiary eruptives and that may belong to the 
same eruptive series as the olivine syenite and anorthosite of Iron Mountain. So 
far as known, these dikes have no economic importance. 

FORM OF THE VOLCANIC NECK. 

It is essential to a clear understanding of the mutual relations of the Cripple 
Creek rocks to remember that the central part of the district is occupied by a 
volcanic neck similar in some respects to those described by Geikie in the south of 
Scotland. At the time of eruptive activity the region seems to have been a granitic 
plateau not differing greatly in the general character of its relief nor even in actual 
surface from the plateau of to-day. The first manifestation of volcanism of which 
there is any record was the formation, by one or more tremendous explosions, of a 
great chasm in this plateau. The granite above the volcanic hearth was shattered 
and blown into the air, falling back as fine fragments partly into the pit formed 
by the explosion and partly over the surface of the plateau. Eruptions of phono- 
lite, latite-phonolite, and syenite followed, but do not appear to have issued in a 
simple sequence. Successive eruptive paroxysms probably shattered and com¬ 
minuted the products of earlier outbursts. The breccia now occupying the greater 
part of the volcanic throat exhibits in many places such a thorough mingling of 


GEOLOGICAL STRUCTURE OF THE DISTRICT. 


25 


different rock fragments as to indicate that the great chasm in the granitic rocks, 
after its initial filling with breccia and intrusive rock, was more than once partly 
or wholly cleared by renewed explosions and refilled with their products. 

These eruptions undoubtedly built up a volcanic cone upon the plateau, but 
the materials of this cone have been removed by erosion very nearly to the original 
plateau surface. Consequently the main central area of breccia shown on the 
geological map more nearly represents a plan of the volcanic throat than it does 
the extent of the former cone. It is important to determine as closely as possible 
how much of this area represents the outline of the deep volcanic chasm or throat 
and how much is merely a residual portion of the practically vanished cone, and 
thus rests upon the old plateau surface. It is also important to ascertain, if pos¬ 
sible the inclination and general character of the contact between the breccia which 
fills the volcanic throat and the granitic rocks through which the eruptive materials 
forced a passage. A convenient plan is to begin in Poverty Gulch, just east of 
Cripple Creek, and thence to trace the outline of the volcanic neck in a circuit past 
Anaconda, Guyot Kill, Elkton, Squaw Mountain, Victor, Bull Cliff, Ironclad Hill, 
and Globe Hill. 

The contact is exposed at several places in the Abe Lincoln mine, in Poverty 
Gulch. For the first 360 feet in depth it seems to have a dip of 80° or 85° S. For 
the next 140 feet the general dip is probably not over 30°. A short distance east 
of the Abe Lincoln mine the Chicago tunnel enters Globe Hill from Poverty Gulch 
and extends eastward to the Plymouth Rock shaft, between Globe and Ironclad 
hills. The tunnel is chiefly in breccia, which near Poverty Gulch is composed 
largely of schist fragments. Lateral branches, however, penetrate solid schist to 
the north and south of the line of the main tunnel. The schist on the north is 
continuous with a mass exposed at the surface in Poverty Gluch. That on the 
south is continuous with the schist exposed at Fairview. The two contacts dip 
toward each other at from 35° to 45°. If these dips are maintained, the Fairview 
and Poverty Gulch schist masses should unite at a depth of from 200 to 300 feet 
below the tunnel. 

In the Midget and Conundrum mines, on the west slope of Gold,Hill, the con 
tact between the ancient crystalline rocks and the breccia is irregular, is at many 
points poorly defined, and has not been exposed in a sufficient number of places to 
fully establish its form and character. All indications, however, point to an increas¬ 
ing steepness of the contact toward the south, and in the Good Will tunnel, which 
passes from granite into breccia somewhat less than a thousand feet south of the 
Midget shaft, the contact is nearly vertical. In the Abe Lincoln and particularly 
in the Conundrum and Midget mines the gneiss is more or less shattered for some 
distance from the contact, and the breccia is largely composed of gneiss and schist 
fragments. 

While the contact as exposed in the Chicago tunnel and in the Abe Lincoln, 
Midget, and Conundrum mines is not so steep as it becomes farther south, the breccia 
of the northwest slope of Gold Hill clearly occupies a pit produced by explosive 
volcanic activity and does not rest in an eroded hollow in the prevolcanic plateau. 
Lying between the main rim of schist and gneiss on the west and the Fairview 
promontory of schist on the east, this pit is apparently a marginal embayment of 


26 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


the central volcanic abyss. Its floor pitches steeply to the south and on an east- 
west line drawn through the summit of Gold Hill may attain a depth of from 1,500 
to 3,000 feet below the present surface. This and other similar embayments in 
the rocks rimming the volcanic neck are doubtless due to the tendency of the vol¬ 
canic forces to find relief in a lateral as well as in an upward direction as the} T neared 
the surface. They may be compared to the flaring enlargements noticeable on the 
side of issue of a bullet hole through plate glass. 

At the Pointer and Mint mines, on the southwest side of Gold Hill, the granite 
and breccia are locally separated by an intrusive mass of syenite. The general dip 
of the pit wall in this vicinity, however, as shown by comparison of its outcrop 
with its exposure in the Ophelia tunnel, is between 70° and 80°. In the vicinity 
of Anaconda and in the Mary McKinney mine the contact between the granite and 
the breccia is nearly vertical, and continues so along its irregular course toward 
Elkton. 

In the Elkton mine the contact between the granite and breccia is well shown. 
North of the Thompson shaft of the Elkton property the contact runs nearly east 
and west, while east of the shaft it runs nearly north and south. This shaft is thus 
situated within a local granite promontory which juts northeastward into the 
breccia of the volcanic neck. The contact as seen in the Elkton mine is irregular 
in detail, but it is clear from its position on successive levels that the promontory 
steeply overhangs the breccia. The granite as a rule shows considerable shattering 
near the contact, which, however, is usually fairly sharp and is too irregular to be 
a fault contact. Fragments of granite are abundant in the breccia, often for dis¬ 
tances of more than 300 feet from the contact. 

Although the original contact between the granite and breccia in the Elkton 
mine is not a fault plane, there has been faulting in the vicinity. The Thompson 
fault or so-called “Dead vein” lies usually just north of the contact. It strikes 
N. 72° W. and dips at 83° S. It is sometimes a simple fissure containing a foot 
or more of soft slickensided gouge, sometimes two or more narrower parallel fissures 
filled with similar material. The throw is apparently normal and the displacement 
probably not more than 100 feet. At a few points, as on level 4, the fault locally 
marks the contact between granite and breccia. The fault is an example, similar 
to others which will be described later, of local movement near the original contact. 
Such fault fissures in most cases more nearly approach a plane surface than does 
the adjacent granite-breccia contact. The breccia had filled the volcanic conduit 
and become somewhat indurated before the faulting took place. 

Between Elkton and Victor the contact passes between Squaw and Battle 
mountains and is approximately vertical. It is well exposed on nearly all the levels 
of the Ajax mine and has in many places been drifted on for considerable distances. 
It is prevailingly steep, dipping north or northeast at angles ranging usually from 
45° to 85°. The average dip is probably between 70° and 75°. Near the shaft, 
particularly on the upper levels, the contact has an east-west course. But, as is 
shown on Pis. II and V, the Ajax shaft is situated in an embayment in the granite 
between the Portland promontor}^ on the east, presently to be described, and 
the northward turn of the contact, which carries it through the saddle between 
Squaw and Battle mountains on the west. This northerly turn is noticeable on all 


u 5.GEOLOGICAL SURVEY 


PROFESSIONAL PAPER NO. 54 PL. V 


PLAN OF PART OF THE UNDERGROUND WORKINGS 

OK THE 

BATTLE MOUNTAIN MINES 

SHOWING VEIN SYSTEMS AND APPROXIMATE t'ONTOURS 
ON THE GRANITE:-BRECCIA CONTACT 
By F L.Ran some 



JULIUS BIEN ft CO.N Y 



















































































































































GEOLOGICAL STRUCTURE OF THE DISTRICT. 


27 


* 


of the Ajax drifts that have followed the contact far enough to the west, and is 
particularly conspicuous on the lower levels. A north-south section through the 
Ajax shaft, showing the steep dip of the contact, is given in fig. 63 (p. 479). The 
apparent flatter dip below level 6 is partly real and partly due to the obliquity of 
this part of the contact to the plane of the section. 

The breccia near the contact- contains abundant fine granitic detritus and fits 
snugly against a wall of granite which is far too irregular to be a fault contact. 
Blocks of granite from 2 to 3 feet in diameter are sometimes found in the breccia 
at a distance of 100 feet or more from the conduit wall. The contact is generally 
sharp and definite, though on account of the granite fragments in the breccia it is 
not everywhere conspicuous. The granite close to the contact is seldom brecciated, 
though in places considerably jointed and even shattered. 

In the Dead Pine mine, just east of the Ajax, the contact has been followed by 
an inclined shaft and found to dip north at 70°. The shaft of the Granite mine is 
in breccia, the various levels all running south across the contact into the granite. 
The general strike of the contact seems to vary from northwest to west, but as there 
are no drifts on it this point can not be accurately determined. The general dip is 
north at about 80°. The contact surface, however, is evidently very irregular, and 
there may be local southerly dips between levels 6 and 7 and between levels 9 
and 10. 

The Portland mine, north of Victor, affords better opportunities of studying 
the inclosing wall of the volcanic neck than any other mine in the district. The 
contact between the granite and breccia is an irregular surface which plunges steeply 
under the breccia to the north and east. Its dip is rarely less than 70°, is frequently 
approximately vertical, and in places forms what would be an overhanging cliff 
were the breccia removed. Some idea of the irregularity and general steepness of 
this contact may be had from PI. V. As is there well shown, the granite in the 
Portland workings forms a bold promontory jutting into the breccia-filled funnel of 
the Cripple Creek volcano. Along the northern scarp of this promontory, west of the 
Portland mine, are the workings of the Granite, Dead Pine, and Ajax mines. Along 
the eastern declivity, south of the Portland, are the workings of Stratton’s Inde¬ 
pendence mine. 

The contact is well exposed on all the Portland levels from the 500-foot to the 
1,000-foot. As a rule it is sharp and readily determined. The breccia for a few 
inches from the granite is hard, rather fine grained, and, as shown by microscopic 
study, is chiefly of granitic origin. It rests snugly against the rather minutely 
irregular wall of granite, which is not as a rule noticeably fractured or shattered. 
Usually there is no evidence of faulting along the contact, and there can be little 
doubt that the breccia was in the main originally deposited in the position it now 
occupies relative to the granite. Occasionally there has been some Assuring along 
planes adjacent and generally parallel to the contact. Such fissure planes, how¬ 
ever, do not follow the irregularities of the actual contact and are not connected 
with extensive faulting. 

On the 500-foot level a sharp contact between granite and breccia is well exposed 
in a short drift on the so-called “Shaft vein,” just west of the Burns shaft. The 
contact here is less steep than is common on the lower levels, dipping north at about 


28 


GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


60°. It may also be well seen about 300 feet southeast of the Burns shaft in a 
crosscut east from the Portland vein. The contact is here sharp, the breccia rest¬ 
ing closely upon an uneven surface of granite. The dip is abnormally low, being 
only about 15°, toward the east. This low dip is undoubtedly local, and if the 
breccia could be removed the granite at this point would probably be found forming 
a relatively flat bench or step with steep scarps above and below. The contours 
of PI. V are strongly indicative of such changes of slope. 

On the 600-foot level the contact, as exposed a short distance north and east 
of the Burns shaft, is definite and close. It is rather irregular, but nearly vertical 
on the whole. Near the Diamond vein, however, about 300 feet east of the shaft, 
the contact is a regular plane dipping about 35° NE. and exhibiting clear evidence 
of some faulting between the granite and the breccia; but the movement is appar¬ 
ently local and not connected with any great displacement. A moderate dip, here 
as on the 500-foot level, obtains on the crest of the granite promontory. It is 20° 
steeper, however, than on the level above, which fact, taken in connection with 
what is known of the contact below, indicates proximity to the outer edge of the 
granitic bench already referred to. 

On the 700-foot level the contact between the granite and breccia is exposed 
in the main drift about 100 feet north of the Burns shaft. It is here sharp and 
close, rather irregular, and as seen in the drift nearly vertical. East of the Burns 
shaft the contact practically coincides with the No. 2 vein. 

On the 800-foot level the contact is in part the east wall of the No. 2 vein. It 
is sharp and irregular in detail. The granite is sometimes shattered for a foot or 
two from the contact, which is here nearly vertical. Toward the north the contact 
soon swings westward, away from the No. 2 vein, and is again well exposed in the 
main northeast crosscut about 125 feet from the Burns shaft. This contact is 
remarkably close and definite and shows no evidence of faulting. Its course where 
cut by the crosscut is nearly north and south and it dips eastward at about 80°. 

On the 900-foot level the contact between the granite and breccia is exposed 
in at least five places. North of the Burns shaft the granite shows some breccia- 
tion near the contact, and the latter is not so sharp and distinct as in other parts of 
the mine. Just east of the No. 2 vein, which is partly within the granite on this 
level, the contact is clearly exposed in a short crosscut. The granite is shattered, 
but not brecciated, for a distance of 2 or 3 feet from the breccia, while the latter 
contains abundant particles of microcline and some small fragments of granite, 
those seen being less than 3 inches in diameter. The contact here dips eastward at 
75° to 80°. A little farther north a crosscut west of the No. 2 vein, which is here 
wholly in granite, exposes a close, definite, irregular, vertical contact of the latter 
rock with the breccia. 

On the 1,000-foot level the contact is exposed about 100 feet north of the 
Burns shaft and along the No. 2 vein. In general it is approximately vertical and 
presents characteristics similar to those observed on the level above. 

The granite-breccia contact is hardly so well exposed in the Independence 
workings as in the Portland. In general it is fairly distinct on the upper levels, 
the granite, as a rule, not showing much brecciation in its vicinity. In detail it 
is exceedingly irregular, being diversified by minor salients and reentrants. The 


GEOLOGICAL STRUCTURE OF THE DISTRICT. 


29 


breccia near the contact is in some cases, as on the 1,400-foot level, so full of granite 
fragments, some of them of large size, that it is difficult to determine in a small 
exposure whether the rock seen is breccia or massive granite. 

While in the Portland mine the contact between the granite and the breccia 
is generally convex toward the northeast, in Stratton’s Independence mine it is 
concave. In the Portland the granite projects into the breccia as a steep promon¬ 
tory; in the Independence the breccia lies in the curved embayment on the east 
side of this jutting point of granite. The benched form of the contact surface 
described in the Portland is also well exhibited in the northern part of the Inde¬ 
pendence embayment. The general dip of the contact is at least 60° N. or NW. 
Further details of this portion of the contact will be found in the description of the 
Independence mine on pages 449 to 465. 

The Golden Cycle shaft, 1,000 feet deep, is wholly in breccia, though the granite 
at the surface is only 1,400 feet distant to the southeast. This shows that the slope 
of the contact must be greater than 35°. 

On Big Bull Mountain the Safety mine, another shaft higher on the northern 
slope of the mountain, and a tunnel and several pits on the northeast side all show 
a nearly vertical contact. Near Grassy Creek there are no deep workings near the 
contact. Its course, as shown on the map, is suggestive of a low angle of dip, and 
a shallow pit on the slope southeast of Cameron indicates that this part of the 
breccia may be merely resting on an old surface of erosion. 

The workings of the New Century, Damon, Jerry Johnson, Sunshine, and 
Iloosier mines, though neither deep nor exclusive, all point to a very steep contact 
along the northeastern border of the breccia area. From Tenderfoot Hill to Car- 
bonate Hill the contact is not explored by deep workings, but a zone of greatly 
shattered granite and schist bordering the fragmental volcanic material is indica¬ 
tive of violent eruptive forces and of a steep contact. At the C. O. D. mine the 
schist-breccia contact is fairly steep. 

The island-like mass of shattered granite which forms parts of Bull and Iron¬ 
clad hills lies almost in the center of the main volcanic area and derives exceptional 
interest from its rather remarkable position. The workings of the Bogart, Sheriff, 
War Eagle, and Ramona No. 2 mines show that to the south the contact of this 
granite with the breccia is steep. This is confirmed by the absence of granite in 
the American Eagle mine, though the bottom level, 1,500 feet deep, extends to 
within 400 feet of a point vertically under the contact at the surface. The char¬ 
acter of the contact on the west, north, and east sides of the mass is unknown, 
though the outline of the granite as shown on the map (PI. II, in pocket) indicates 
a high angle of dip. 

Granite, unfractured and with a steep contact surface, appears on level 11 of 
the Isabella mine, about 800 feet vertically below the Emma No. 2 shaft house. 
This granite is of the Pikes Peak type, however, while that of the Bull Hill area 
and of the tongue which extends west of Cameron is of the Cripple Creek type. 
Whether this body of granite occurring at so great a depth represents the crater 
wall, of which the average slope from the surface down is in such case not much 
over 45°, or whether it is a huge fragment which parted from the side of the chasm 
above and sank into the pit, it is impossible to say. 


13001—No. 54—06-4 



30 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

The general conclusion reached regarding this principal breccia mass, extending 
from Goldfield to Carbonate Hill and from Guyot Hill to Cameron, is that it occupies 
the throat of the main volcano. This is certainly true of the breccia between Gold 
Hill and Goldfield and between Victor and Altman. Whether the pit filled by this 
breccia is continuous with that north of Ironclad and Gold hills is not established, 
owing to the lack of deep workings at the head of Squaw Gulch. It may be that 
the schist mass of Fairview and the Granite mass of Bull Hill come together at a 
moderate depth and that the breccia of Globe Hill fills a separate vent, which only 
superficially coalesces with the great chasm to the south. 

Of the form of the outlying breccia masses, including those of Mineral Hill, 
Rhyolite Mountain, Copper Mountain, and Mount Pisgah, less is known. Though 
the breccia in some places, as just north of the city reservoir in Cripple Creek, seems 
to rest upon a surface of erosion, in most cases it has steep contacts with the older 
rocks, and appears to fdl local vents. On the east side of the Mineral Hill mass, for 
example, the. contact as shown by the Aztec shaft, 60 feet deep, dips 45° W. A 
steep dip is indicated also by the relation of the contact to the topography on the 
northeast side of the hill (PI. II). 

At the Fluorine mine, on Copper Mountain, the breccia rests on a gentle slope 
of granite, but contains great fragments of the underlying rock, showing that the 
source of the breccia is near. 

BRECCIA. 

LOCAL BEDDING. 

The general form and geological occurrence of the breccia have been partly 
outlined in the preceding section. The formation occurs mainly in the principal 
volcanic neck. There are, however, a few outlying masses, some of which seem to 
fill local volcanic vents, while others appear to be residuals of the formerly more 
extensive accumulations of breccia that lay upon the uneven surface of the pre- 
volcanic plateau. 

As a rule, the volcanic breccia is a structureless agglomeration of fragments, 
varying in the character and size of its constituent materials from place to place, 
but showing no stratification and no definite arrangement of its particles. There 
are a few notable exceptions to this rule, however. In parts of the Captain stopes 
and in the southwest part of the 220-foot level of the Portland mine the breccia, 
which in these places is rather fine grained, shows well-marked banding due to the 
alternation of layers of relatively fine and coarse material. On the 220-foot level, 
where these layers are best shown, they are about a foot in thickness and the mate¬ 
rial resembles nearly horizontally bedded grits or coarse sandstones. This bedded 
structure, however, is never continuous for long distances and the bands pass grad¬ 
ually into the usual unstratified breccia. Similar nonpersistent stratification occurs 
at a few places in Stratton’s Independence mine, in the southeastern drifts of the 
Isabella mine, in the Lucky Guss No. 2 mine, on the south slope of Bull Cliff, on the 
slope south of Cameron, and in the Elkton mine. A bed of very fine-grained, 
loose volcanic ash is exposed in the shallow Red Rock shaft near the Hoosier mine. 
In the Elkton the bands dip at about 40°. The lack of sharpness and persistency 
and the various attitudes in which this stratification occurs indicate that the sorting 


GEOLOGICAL STRUCTURE OF THE DISTRICT. 


31 


and arrangement of the material was not effected in a body of water, which, indeed 
could hardly have existed within the conduit during the volcanic period. It would 
rather seem to be due to the winnowing action of winds on material thrown into 
the air, to a sorting by rolling down slopes, or to alternations in material thrown 
out by successive eruptive explosions. 

CARBONACEOUS MATERIAL. 

In the Doctor-Jackpot mine, just above level 15, or about 600 feet below the sur¬ 
face, the ore is accompanied by a black coaly material, of rather fragile character, 
which retains an original woody structure. Chemical examination of this material 
by Doctor Hillebrand shows that it is noncoking, gives an oily distillate, and is a 
bituminous coal with the following composition: 

Composition of coal from Doctor-Jackpot mine. 


Moisture. 1.0 

Volatile carbon.. 29. 0 

Fixed carbon. 68. 4 

Ash. . 1.6 


100.0 

Similar material, but with conchoidal fracture and no trace of an originally 
organic structure, occurs in irregular bunches in the breccia on the 550-foot level 
of the Morning Glory mine, particularly near the west end of the Ingham crosscut. 
This is also noncoking and its composition is as follows: 

Composition of coal from Morning Glory mine. 


Moisture... 0.5 

Volatile carbon. 21. 0 

Fixed carbon.:. 69. 9 

Ash.. 8.6 


100.0 


Rickard" mentions the finding of similar coaly material in the Logan mine at a 
depth of 600 feet and of a silicified tree stump in the [Stratton’s] Independence 
mine at a depth of 500 feet. In July, 1905, a carbonized tree trunk was found on 
the 800-foot level of the Elkton mine. A letter from Mr. E. M. De la Vergne, the 
manager of the mine, dated November 25, 1905, states that the log is 18 inches in 
diameter and was at that time exposed for a length of 5 feet. It lies in hard 
unfissured breccia, about 40 feet west of the Elkton basic dike, and the matrix 
shows the impressions of knots and bark. A specimen from this tree trunk, kindly 
supplied by Mr. De la Vergne, retains the rings of growth and other general woody 
structures, although the material is now altered to coal like that found in the 
Doctor-Jackpot mine. According to Prof. F. H. Knowlton the tree was undoubt¬ 
edly a conifer and probably belonged to a species of Pinus. 

In view of these various occurrences there c^n be no question that vegetation of 
the time of the Cripple Creek eruption was buried in the breccias to depths which, 
after erosion, are still to be measured by several hundreds of feet. This fact, more 


a The Cripple Creek volcano: Trans. Am. Inst. Min. Eng., vol. 30, 1900, p. 384. 














32 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


than any other, helps us to realize the force of the explosions that brecciated the 
rocks and the thorough mixing of the shattered material, whereby trees and pre¬ 
sumably weathered surface rocks could be so deeply entombed. Such mixing 
could scarcely take place unless the materials now filling the volcanic neck had been 
actually blown into the air, leaving a great pit into which they fell back in chaotic 
confusion. The position of this carbonaceous material affords material support to 
the view, presented in subsequent pages, that the Cripple Creek ores were deposited 
at a very moderate depth; or, in other words, that the post-volcanic erosion has 
effected little more than the reduction of a comparatively small volcanic cone. 

The presence of charred or carbonized wood is by no means uncommon in 
volcanic necks, and has been recorded by Archibald Geikie® in those of Scotland and 
by Cross b in the agglomerate of the Bassick neck in Custer County, Colo. 

INTRUSIVE MASSES WITHIN THE VOLCANIC NECK. 

The breccia, which constitutes the main filling of the volcanic funnel, incloses 
a number of masses of latite-phonolite and of syenite. These bodies are largest 
and most abundant in the part of the central breccia area lying between Victor and 
Cameron—that is, in the southeastern part of the volcanic neck. They are generally 
of very irregular shape and are undoubtedly in most cases intrusive into the breccia. 
Sharp contacts, however, seldom occur, as the adjacent breccia is often composed 
of fragments identical in petrographic character with the massive rock, and the 
massive rock itself is in many places greatly shattered. It is conceivable that 
some of these masses are remnants of larger intrusions solidified early in the volcanic 
period and partly shattered by later eruptions. 

The syenite occurs only within the main breccia area. The largest mass, 
which is inseparably involved with latite-phonolite, is at the south end of the town 
of Independence, and with other bodies exposed in the workings of the Vindicator 
mine. A smaller mass lies just west of the Vindicator body and is exposed under¬ 
ground in the Last Dollar mine. A third intrusion is mapped on the north slope of 
Battle Mountain and has been reached underground in the workings of the Portland 
mine. A fourth mass occurs at the Pointer mine, on the southwest slope of Gold 
Hill, and a fifth near the Logan mine, on Bull Hill. 

In Poverty Gulch are two dikes which were shown as andesite on the first 
geological map of the district. Though decomposed, they seem to be mainly 
syenite with perhaps some latite-phonolite facies. The longer dike is exposed in 
the workings of the Molly Kathleen mine, on the south slope of Tenderfoot Hill. 

The Vindicator syenite mass, which in -all probability consists really of several 
masses associated with latite-phonolite, gives place on the lower levels of that mine 
to latite-phonolite which is known to be continuous with the latite-phonolite of the 
Golden Cycle mine, north of Goldfield. The Last Dollar syenite body continues to 
at least 1,200 feet in depth, but shows many local gradual transitions to latite- 
phonolite. On the whole, latite-phonolite predominates underground in the Last 
Dollar and is probably connected with the syenite and latite-phonolite of the Vin- 

a On the Carboniferous volcanic rocks of the basin of the Firth of Forth—their structure in the field and under the 
microscope: Trans. Roy. Soc. Edinburgh, vol. 39, 1880, p. 471. 

b Geology of Silver Clifl and the Rosita Hills, Colorado: Seventeenth Ann. Rept. U. S. Geol. Survey, 1896, pt. 2, p. 311. 






GEOLOGICAL STRUCTURE OF THE DISTRICT. 


33 


dicator and Golden Cycle mines. The Battle Mountain syenite and latite-phonolite 
are also facies of a single intrusive mass. 

The latite-phonolite occurs mainly as irregular stock-like bodies or in thick 
sheets. A good example of the former type of occurrence is found in a biotitic 
variety (biotite trachyte) which is exposed over a large part of the northern slope of 
Battle Mountain and in the workings of the Portland and Dead Pine mines. The 
No. 3 shaft of the Portland mine was started in this rock and continued in it to a 
depth of about 1,000 feet. It then passed out of the latite-phonolite into breccia, 
the irregular contact between the two rocks here dipping to the west. A narrow 
tongue of the latite-phonolite passes through the saddle of Battle Mountain, extends 
southward nearly to the granite, and is reached in some of the western workings of 
the Portland mine and in a northeast crosscut in the Dead Pine mine. This intru¬ 
sive body was described by Cross as a mica andesite, but on account of its unsatis¬ 
factory surface exposures was not mapped by him. Underground workings have 
since thrown considerable light upon the shape and extent of this intruded body. 

Another irregular mass of latite-phonolite which sends out a number of dike 
apophyses lies between Battle Mountain and Goldfield. This rock was mapped by 
Cross as augite andesite and was thought to be a remnant of an early surface flow 
that had been partly brecciated by later volcanic explosions. It has not been so 
well exposed underground as the micaceous facies of Battle Mountain, but has been 
cut at a sufficient number of places in the Portland and Independence mines to 
demonstrate its irregular intrusive character. The adit level of the Portland mine 
is in this rock for about 1,000 feet from the portal. Owing to the general eastern dip 
of its western contact, the latite-phonolite lies to the east of the principal Portland 
workings on the 500-foot and lower levels. It occasionally shows syenitic facies. 

The large area of latite-phonolite extending from Bull Ilill to the saddle north 
of Battle Mountain, though connected with dikes, seems to be in the main a thick, 
irregular intrusive sheet. The shaft of the Blue Bird mine penetrates this sheet and 
passes into breccia at a depth of from 300 to 400 feet. The same relation is shown 
in the Dante, Gold Sovereign, and other mines in the vicinity, which at depths of a 
few hundred feet at most pass out of latite-phonolite into breccia. The flat bottom 
of the sheet is exposed also in the Lower Trail tunnel in Arequa Gulch, above Elkton. 
The mass of latite-phonolite reaching from Independence to Altman also lias a nearly 
horizontal under contact near the Shurtloff No. 2 shaft, which is reported to pass 
into breccia at a depth of about 500 feet. On the east side of the mass, however, the 
workings of the Dead wood No. 1 mine show the contact to be nearly vertical for a 
depth of at least 300 feet. 

The shape of the large body of latite-phonolite that underlies the town of Altman 
and extends down through Independence is unknown. The southwest contact of 
the mass with the breccia is very steep at the Findley mine, for on the 900-foot level 
syenite (probably the equivalent of the latite-phonolite on the surface) is reached 
130 feet east of the shaft. 

The contact of the breccia with the latite-phonolite or syenite, between the 
Vindicator and Lillie shafts, is almost vertical for a depth of 1,000 feet. No breccia 
has been found underneath the Vindicator area of syenite. In all of the lower levels 


34 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


of the Vindicator latite-phonolite prevails, but it contains two or three smaller 
masses of syenite which are usually separated from the latite-phonolite by sharp 
contacts, although in some places there is a gradual transition. 

A very persistent dike of latite-phonolite traverses the breccia in the Hull City 
mine, from the massive rock in the Vindicator to some point in the Findley ground. 

The Zenobia and Pharmacist mines show that the large mass of latite-phonolite 
north of Altman is overlain on its western side by breccia. The arm extending from 
the main mass to Bull Cliff is exposed in the Isabella mine where, at a depth of about 
1,000 feet, it contracts rather rapidly to a narrow dike. 

Little is known of the shape of the intrusive masses of Big Bull Mountain, as they 
are unexplored by deep mines. 

Two masses of latite-phonolite are exposed on the south slope of Gold Hill and 
in the workings of the Anaconda mine. The eastern mass was mapped by Cross as 
syenite porphyry, while the western one was represented by two separate dikes of 
andesite. A mass of latite-phonolite of unknown size is cut in a west crosscut from 
the Anaconda tunnel toward the E. Porter Gold King mine, but this body is not known 
to reach the surface. Like the' two occurrences mapped it is apparently intrusive 
into the breccia, although the contact is, as usual, rather indefinite. 

As has been already noted, the syenite usually shows gradations into latite- 
phonolite, indicating that the two rocks are facies of a single intrusion of magma. 
In some places, however, as in the Vindicator mine, the two rocks are in eruptive 
contact, showing that one facies had solidified before the intrusion of the other. It 
is not always clear, in such cases, which is the later rock. 

The peculiar trachydolerite of Bull Cliff is probably an intrusive sheet whose 
upper surface has been uncovered by erosion. It is clearly younger than the latite- 
phonolite and is probably younger than the latest eruption of phonolite; but it 
is older than the basic dikes described in a subsequent section. 

OUTLYING INTRUSIVE MASSES. 

While the intrusive masses (exclusive of small dikes) in the breccia of the vol- 

t 

canic neck are nearly all syenite and latite-phonolite, the outlying intrusions derived 
from the Cripple Creek volcanic center are nearly all phonolite. In most cases, as 
on Pisgah, Rhyolite, Copper, Trachyte, and Straub mountains and on Grouse Hill, 
the phonolite bodies of considerable area seem to have the form of irregular sheets, 
which, however, may be merely the upper expanded parts of plug-like intrusions. 
These sheet-like bodies are sometimes directly connected with dikes. Between 
such sheets and the phonolite dikes later described no sharp distinction can be made. 
The phonolite sheets are rarely associated with important deposits of ore. 

The phonolite mass of Beacon Hill is an eruptive plug filling an elliptical con¬ 
duit in the Pikes Peak granite. As this plug is encircled by productive ore deposits 
it has been exposed at a number of points in the El Paso, Gold Dollar, and smaller 
mines in the vicinity. The contact dips steeply into the hill, the average angle being 
near 75°. If this dip should continue downward at the same angle, the bottom of 
the phonolite would be found at an approximate depth of 2,200 feet. The walls of 
the conduit, however, are likely to become steeper or more irregular at greater depth. 


U. S. GEOLOGICAL SURVEY 


PROFESSIONAL PAPER NO. 5+ PL. VI 



A. VICTOR, FROM SQUAW MOUNTAIN. 

The shaft house of the Gold Coin mine is in the left foreground, and that of the St. Patrick mine in the middle-ground. 



B. BATTLE MOUNTAIN MINES, FROM SQUAW MOUNTAIN. 
Goldfield is in the distance, with Big Bull Mountain and Pikes Peak on the sky line. 









GEOLOGICAL STRUCTURE OF THE DISTRICT. 


35 


The contact is usually sharp and in many cases minutely irregular. In places, 
particularly on the west side of the hill, the granite is only slightly brecciated at the 
contact. Elsewhere, as in the Gold Dollar mine, the two massive rocks are sepa¬ 
rated by as much as 15 feet of breccia composed of mingled fragments of phonolite 
and granite. In the open cut and stopes of the Prince Albert mine, on the east side 
of the hill, bodies of similar breccia are inclosed in the phonolite. 

The orifice now sealed by the phonolite was probably formed by a local explo¬ 
sive eruption and was partly filled with breccia, this breccia being subsequently 
forced out and replaced by the intrusion of the massive phonolite. It is possible 
that greater erosion of the district would expose similar plugs which are now capped 
by thick irregular sheets. 

DIKES OF THE VOLCANIC PERIOD. 

The breccia and latite-phonolite and the surrounding pre-Cambrian rocks are 
cut by abundant dikes of phonolite, ranging in width from a few inches to 400 feet. 
While many of these phonolitic dikes belong to late phases of the eruptions, much 
phonolite was erupted at earlier periods and these masses contributed their frag¬ 
ments to the final breccia produced by the volcanic explosions. The diversity in 
age of the phonolite intrusions is shown by one phonolite dike cutting another, as 
may be seen half a mile east of Galena Hill, or by phonolite dikes cutting breccia 
composed of phonolite fragments, as may be seen in the mines of Raven Hill. In 
a general way there is a rough radial arrangement of the phonolite dikes around the 
main volcanic neck; but the dikes are often exceedingly irregular and not all of 
them conform to this plan. 

The number of these dikes is vastly greater than can be indicated on a geolgo- 
ical map of the scale used in this report. They are found in practically all the 
mines of any size and in many cases do not appear at the surface. They can be 
studied to particular advantage in mines situated in the granite, such as the Gold 
Coin, Dead Pine, Granite, and Independence, their green-gray color and aphanitic 
texture contrasting much more strongly with the granitic rocks than with the 
volcanic breccia. In the Gold Coin mine the remarkable irregularity of some of 
the dikes is clearly shown. They branch and coalesce; they swell and pinch out; 
they change abruptly in course and dip; or they turn sharply into irregular, nearly 
horizontal sheets, in some cases resuming the vertical dike-like form a few feet 
away. 

The phonolite dikes are of much economic importance in the Cripple Creek 
district, as will be pointed out in the section devoted to the ore deposits. 

The last eruptions from the Cripple Creek volcanic center were the basic dikes. 
Like the phonolite dikes, they show a certain tendency to radiate from the central 
part of the district. They are less abundant, however, than the phonolite dikes 
and apparently nowhere extend more than 2,000 feet from the volcanic neck, 
while most of them are found within the breccia. Generally nearly vertical, few 
of them are over 5 feet wide and they are usually fairly regular in trend. They 
occur characteristically in zones, of which the individual members seldom continue 
for long distances. Usually as one dike of such a zone pinches, another appears 
in a parallel fissure a few feet away. In some places the two dikes are seen to be 


36 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


connected; in others they appear to be entirely separate. The basic dikes decom¬ 
pose readily and are not well exposed except in the mines. Though many of them 
have no known connection with ore deposits, others, such as the Elkton-Raven, 
Conundrum, Strong, Anna Lee, North Star, Dolly arden, Pinto, and Block 8 
dikes either contain ore or are closely associated with ore bodies in other rocks. 

TOPOGRAPHIC DEVELOPMENT. 

INTRODUCTION. 

Erosion in its various forms is at the present time the only agent of importance 
that is shaping the topography of this district by sculpturing its surface. But 
during past times constructive as well as destructive forces were at work, and 
during the epoch of eruptions the former were of sufficient intensity to over¬ 
come the work of the latter by building mountains of tuffs and ashes and lavas, 
which erosion again is in a fair way to obliterate. It is difficult to trace the 
physiographic history of a small district without going beyond its borders, and yet 
a little light may be thrown on the subject by a study of the surface forms near 
Cripple Creek. 

In attempting to trace the topographic development we shall find it impossible 
to go further back than to the time just antedating the volcanic eruptions, that is, 
the middle or end of the Tertiary age. The inquiry resolves itself into three parts: 
(1) What were the surface forms previous to the volcanic eruptions? (2) What 
were the surface forms at the close of the volcanic epoch? (3) What changes have 
been effected since that time? 

PREVOLCANIC CONDITIONS. 

Broadly regarded, the region is an undulating plateau, a truncated upland 
with elevations of from 9,000 to 10,000 feet, above which some points rise to indi¬ 
vidual prominence. This plateau is deeply scarred by the abrupt canyons of Oil 
and Beaver creeks, which drain southward into Arkansas River.® In the local 
area this plateau finds expression in the rolling hills southwest of Cripple Creek and 
in Beaver Park in the northeast corner. The individual hills rising above this are 
represented by Trachyte, Rhyolite, and Big Bull mountains, and the volcanic 
complex of hills clustering about Bull Hill. The incised canyons are represented 
by Wilson Creek, Cripple Creek, and Spring Creek. If it were always possible 
to distinguish between intrusive and effusive igneous contacts the task of mentally 
restoring the prevolcanic surface would be much easier. No decisive evidence 
regarding this surface is offered by the whole southwestern contact line of breccia 
and granite. But on Big Bull Mountain, along Grassy Creek, and on parts of 
Carbonate and Mineral hills, as well as on Copper Mountain, there is some good 
evidence that the breccia rests in general on an old surface of granite and other 
rocks. It is inferred with some certainty that Big Bull Mountain existed as a 
rather prominent point in prevolcanic times, and that undulating hills along the 
north side of Grassy Creek and the summits of Tenderfoot and Carbonate hills 
formed part of this prevolcanic surface. The points mentioned belong to the 


a See Geologic Atlas U. S., folio 7 (Pikes Peak), U. S. G • i. Survey, 1894. 






GEOLOGICAL STRUCTURE OF THE DISTRICT. 


37 


hr- 

5 


o 

CD 

O 

o' 

13. 

CD 

- 


P 

B 

Cu 


•-I 

P 

C 

o* 

£ 

o 

5 

s 

a 

w 

er 

o 

$ 

S' 

<w 


so 

S3 


So 

r> 


a 

a. 

33 

o 

u> 

T* 

< 

o_ 

o' 

P 

3 

o' 

o 

-1 

o 

£ 2 . 

o' 

a 


r O 


\ 1 

CC\ KS> 


A 

A 

5 

o 


o 

o 


o.\o 


o 

Cn 


°Mo 

\ N ) 

y/J 

o 

o 

o 

O 

O 



■ym 




o 

-I 

o 

c 

01 

Cl 


ST 

o 


general plateau referred to above and the coincidence suggests that this plateau 
is of prevolcanic age. Still better evidence is obtained from 
certain detrital deposits which belong to the volcanic epoch or 
to the one just preceding it. In the city of Cripple Creek, at 
the reservoir, situated on a spur of Mineral Hill, at an eleva¬ 
tion of 9,600 feet, lies a small deposit of nonvolcanic conglom¬ 
erate with large waterworn bowlders of granite, gneiss, and 
diabase (p. 22); it is not more than 50 feet thick and is appar¬ 
ently overlain by the breccia which caps the spur north of the 
reservoir. There is good reason to consider this as pre¬ 
volcanic gravel filling a depression in the general surface of 
the plateau, whose antecedent slopes rise gently on the north, 
east, and west to a height of several hundred feet, while the 
natural outlet of the hollow would have been southward or 
perhaps into the area now occupied by volcanic rocks. 

On Straub Mountain and Grouse Hill rest detrital rocks of 
granitic origin with a maximum thickness of 150 or 200 feet. 

They are poorly sorted, consist mostly of sand and fine gravels, 
and are believed to have been deposited as a result of the 
first explosive action preceding the actual volcanic outflows. 

(See p. 22.) Flat bodies of phonolite are intrusive in these 
sands, and as shown on Grouse Hill were once covered by 
them to an unknown elevation. As shown in fig. 2, which is 
an east-west section through Brind and Straub mountains 
and Grouse Hill, these deposits rest on an even surface gently 
sloping westward and rising more rapidly northward. The 
lowest point of their underlying surface is on the west side of 
Grouse Hill, where its elevation is 8,950 feet. To the south the 
basal granite rises again very gently, as seen from the contour 
lines in the Pikes Peak folio, so that there exists here a dis¬ 
tinct depression, the upper continuation of which most likely 
should be traced through the flat amphitheater of upper Wilson 
Creek and into the volcanic area at Victor between Big Bull 
and Squaw mountains. From here one branch probably con¬ 
nected with the upper amphitheater of Cripple Creek, in the 
center of which lies the gravel deposit referred to above, while 
another one seems to have headed northward, passing by 
Cameron and having its source in the plateau about Gillett. 

To sum up, there is good evidence that the surface of 
this area as it was in the last part of the Tertiary period is 
well represented by the irregular granitic plateau with general 
elevations of 9,500 to 10,000 feet, which, though greatly dis¬ 
sected, now extends to the south and southwest of Cripple 
Creek. The undulating country of Beaver Park plateau about 
Gillett belongs to this plateau. The erosion effected in it by 
the present Beaver Creek probably does not amount to more 
than 100 feet. Above this plateau rose flat-topped hills such as Big Bull Mountain, 


h 

\\-l5 

Yu 


' - it* V 

- ' At ~ 

l ' 


' G'vt ° 

\ o 




ti 




V «' 


N I s/ 


/S / - It 

I . 1 


z 
o 
(/> 
> 

i i 
vm ; g 

\ - " 'v. > 

- \N |T3 < 

Y k P 
As p-fe £ 

-/''I 5 
' o 

3 \, i ■ 

V z Y 9 
/ - _ 10) 


\ \ 
\ 


I (A 

'5 

Y>\'^ 




✓ — s 

/. ^ \ z \ 

CYYo-7 s 

^ i ^ n -i 1 rn 









38 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


Cow Mountain, and the several projecting shoulders of Pikes Peak. Other emi¬ 
nences like Trachyte, Rhyolite, and Brind mountains may also have had a similar 
form before erosion, attacking them from several sides, had sharpened their 
summits. This truncated topography probably resulted from the long-continued 
action of erosion; the plateau is regarded as a peneplain; its higher summits may 
possibly be remnants of an older and higher plateau. 

EPOCH OF CONSTRUCTION. 

This lofty, rolling granitic plateau became, in middle or late Tertiary time, the 
scene of intense volcanic activity. Violent explosions with almost inconceivable 
force blew a hole through the granite, scattering its debris over the surrounding 
country. A remnant of this detritus is still believed to be preserved at the lowest 
outlet of the prevolcanic drainage on Grouse Hill and Straub Mountain. Repeated 
explosions filled the volcanic neck with breccias, and the result was the upbuilding 
of a volcanic cone on the granitic plateau. Final intrusions of phonolitic magmas 
occurred in the breccia, in the surrounding granite, and even, as on Grouse Hill and 
Straub Mountain, in the granitic debris. The question may now be asked, What 
was the height of this cone? This query has more than academic interest, for 
another highly important question hinges on this point, namely, At what depth 
below the surface were the gold-bearing veins formed ? 

Recognizing the fact that the sections (PI. II, in pocket) of the present topog¬ 
raphy entirely fail to represent the volcanic mountain which must have existed, 
and that near the summits of the Amlcanic hills are intrusive bodies of granular 
rocks, we may conclude that a great part of the accumulated lavas and breccias 
and tuffs have been carried away. The height of the mountain must have been less 
than one-third the diameter of its base. The steepest slopes of large volcanic cones 
are rarely over 30° and toward the base the slopes become very much less steep. 

If the summit attained 15,000 feet—about 5,000 feet above the present highest 
elevation—the base of this cone must have had a radius of at least 5 miles and 
probably very much more. As the prevolcanic surface is reasonably well preserved, 
we should expect to find breccias and tuffs—at least in small patches—scattered 
over the plateau, especially in the slightly eroded basin of West Beaver Creek near 
Gillett. This is not the case. The breccias and phonolite found outside of the 
main area are very clearly due to local eruptions. Hence an original elevation 
of 15,000 feet seems improbable. On the other hand, the phonolite of Grouse Hill 
is evidently an intrusive sheet in the granitic detritus now underlying it, and small 
patches of the same granitic sand are found on the summit of the phonolite. Hence 
we are justified in concluding that a thickness of at least several hundred feet of 
volcanic material once rested on top of this phonolite. From a tentative recon¬ 
struction of the cone as shown in fig. 3, it would seem as if its summit could scarcely 
have exceeded 13,000 feet. On this basis the vicinity of Victor would have been 
covered to a depth of about 2,000 feet and Bull Hill to a depth of about 2,500 feet. 
While these figures are merely tentative, they clearly show that it is very improba¬ 
ble that of 5,000 or 10,000 feet of volcanic material have been eroded—a conclu¬ 
sion that is strongly supported by the occurrence of carbonaceous material in the 
breccia as described on page 31. 


GEOLOGICAL STRUCTURE OF THE DISTRICT. 


39 


EPOCH OF DESTRUCTION. 

Since the volcanic forces ceased, 
erosion has had full sway to destroy 
what they built up. It is natural that 
volcanic cones should fall an easy prey 
to the action of atmospheric agencies, 
and their destruction is usually early 
and complete. But a special reason 
contributed to render this process un- 5 
usually rapid in this case. Before the “ 
volcanic epoch the streams flowing on f 
the plateau were sluggish in their action § 
and slight in grade. After that epoch g. 
there occurred a general elevation of | 
several thousand feet, whereby the old ” 
peneplain became a high plateau. The 1 
causes of this elevation, as well as its §• 
exact extent, can not be discussed here; g 
their consideration properly belongs to § 
the study of a wider area. At any rate g 
the streams became rejuvenated and ® 
began to cut back rapidly into the pla- |' 
teau, especially from the southern side, ® 
belonging; to the drainage of the Arkan- 3 
sas. To this Quaternary and still active < 
epoch of erosion must be credited the § 
deep canyons of the several branches % 
of Cripple Creek, Spring Creek, and § 
Wilson Creek. The canyon of the lat- g 
ter between Grouse Hill and Straub ® 
Mountain is an especially well-marked 1 
and striking case. That the branches ~ 
of Cripple Creek and Spring Creek have ® 
also eroded their canyons below the pla- I 
teau surface in comparatively recent | 
time is very evident from even a cur- ■§ 
sory study of the contour map. 

There is no evidence of a glacial 
epoch within the Cripple Creek district 
except in the northeast corner of the 
area, where the glaciers from Pikes 
Peak reached down and pushed their 
moraines almost to Gillett. That the 
glacial epoch had some influence on the 
topography of this vicinity is certain. 




SECTiON CC 































40 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


It seems probable that before the glaciation the basin near Gillett drained north¬ 
ward into Oil Creek (see Pikes Peak folio), but that later this drainage was 
diverted southward to West Beaver Creek. 

The drainage of the volcanic area presents some interesting features. A 
fairly uniform volcanic cone will immediately develop a radial drainage system 
which is very apt to be superimposed upon the underlying rocks when these are 
reached by erosion. This kind of drainage is in fact indicated by Wilson Creek 
above Goldfield, by Arequa Gulch, and by Squaw Gulch, but to the north and east 
there is no indication of such a radial drainage. This shows, we believe, that the 
volcanic cone was not symmetrical, the southwest slope being much more prominent 
than the others, and also that the horizontal extent of the base of the volcano was 
probably confined within the limits of the special map. Had the deposits covered 
Big Bull Mountain and sloped uniformly eastward, gulches leading in that direction 
would surely have been established. The southward turn of upper Wilson Creek 
at Goldfield indicates that Big Bull Mountain existed at the close of the volcanic 
epoch and that it diverted the course of the gulch to correspond to an old pre- 
volcanic drainage channel. On the north slope toward Cameron there are no indi¬ 
cations of deep gulches in the volcanic area and it seems very unlikely that Grassy 
Creek, which in its flat course shows little evidence of the rejuvenating influence 
of the uplift, could have been established had not a slight depression existed 
between the volcanic hills and the granitic ridge west of Calf Mountain. 


CHAPTER III.—DESCRIPTION AND PETROLOGY OF THE META- 

MORPH1C AND IGNEOUS ROCKS. 

By L. C. Graton. 

INTRODUCTION’.« 

PLAN AND SCOPE OF THE INVESTIGATION. 

The rocks of the Cripple Creek district were made the subject of an extended 
petrographic study by Mr. Whitman Cross in connection with his examination of 
the geology of the region in 1894. At that time mining developments in the district 
were only well begun, and the geological worker had in most cases to be content 
with such information as could be derived from natural exposures. For various 
reasons—forest covering, presence of soil and slide, and in many cases profound 
decomposition of the rocks—the data thus obtained were in large part meager and 
unsatisfactory. Decomposition caused most trouble in the most critical portion of 
the district—the volcanic area—and made particularly difficult of attainment a 
good knowledge of the breccia and the basic dike rocks. In spite of these facts, 
that portion of Mr. Cross’s report 6 which deals with the description of the rock 
formations not only gave the first insight into the nature and relations of these 
extremely interesting rocks, but furnished an excellent conception, broad and at 
the same time detailed, of the petrology of this district. His work is so well known 
to petrographers that further comment is hardly necessary. 

The present investigation was conducted under much more favorable circum¬ 
stances. That portion of the district which is of greatest petrographic importance 
is now prospected to a degree probably unequaled elsewhere. Developments rang¬ 
ing from shallow pits and trenches to very extensive mine workings actually honey¬ 
comb the rocks near the surface. These openings in several ways lend aid to the 
study of the geology and petrology. They furnish definite, satisfactory exposures 
of the rocks; they enable fresh material to be collected almost at will, and the 
deeper workings, reaching in some cases to a depth of 1,500 feet, afford an under¬ 
standing of structural relations which no amount of surface study could give. With 
the conclusions reached by Cross already in hand, more attention could be given 
to details in this later work. Furthermore, a somewhat greater length of time was 
available for this examination than was at the disposal of Mr. Cross. Finally, this 

a The writer wishes to acknowledge his obligation to the authors of this report for their unfailing interest and cooperation 
in his work. He owes much to Mr. Ransome for suggestions and helpful criticism both in the field and in the office. The 
larger part of the office work has been done under the direct supervision Of Mr. Lindgren, for whose advice, criticism, and 
aid he is deeply indebted. To both these gentlemen are due his thanks for the opportunity to study and describe this most 
interesting group of rocks. The value of this chapter has been much increased by a careful criticism by Mr. Cross. 

b Sixteenth Ann. Rept. U. S. Geol. Survey, pt. 2, 1895, pp. 20-58. 


41 








42 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

report is not only based on the studies of the writer, but also embodies those results 
of the extended investigations of Mr. Lindgren and Mr. Ransome which have a 
bearing on petrography. 

Under these advantageous conditions the w r ork w r as carried on so far as possible 
independently and as if original, and it is gratifying to know that it sustains the 
main conclusions of Mr. Cross. On the other hand, results which differ from his 
have been obtained in some instances and considerable that is new has come to light. 
Such differences, however, are in many cases unessential and may often be explained 
by the difference in conditions of w r ork already noted. 

While the present account of the petrology of the district thus comprises much 
that is contained in the earlier report, it has been deemed advisable to present it in 
full. This decision has been largely based on the fact that the early report is out 
of print and also on the belief that this independent verification of Cross’s principal 
results can not fail to add to then* value. Moreover, an adequate presentation of 
such features as are new and different can hardly be given without a full statement 
of the results common to both investigations. 

The essentially economic character of the study of which the petrology is but a 
part has rendered it desirable that the conclusions reached and the distinctions 
recognized in the mapping and in the petrographic descriptions be of practical 
application not only by the experienced petrographer but by the miner as well. 
Minor variations within rock masses or among different bodies of the same general 
type have consequently not been made prominent, though they have been noted 
and described. While this desideratum has been borne in mind, it has, neverthe¬ 
less, been the endeavor to make the treatment scientifically accurate and to bring 
out such petrologic principles as are exemplified by the rocks. It may not be inap¬ 
propriate to state that the descriptions and conclusions here given are based on a 
study of the large collections of rocks, with numerous thin sections, from the Pikes 
Peak quadrangle and the Cripple Creek district made by Mr. Cross and kindly placed 
by him at the writer’s disposal, and also of the specimens, numbering about 750, 
with very many thin sections, collected during the resurvev of the district. Each 
rock type is thus very well represented, and nearly all the important rock, masses 
have been studied by means of numerous specimens. It has been sought throughout 
to make this a study of geological units—rock masses—instead, as is so often the 
case, of particular, individual hand specimens. It is believed that the large number 
of specimens lias made possible a fairly satisfactory achievement of this aim. 

In view of the close relation existing between the processes of rock alteration 
and those of ore deposition, especial attention has been given to the subject of 
decomposition and alteration of the mineral components of the rocks. 

OUTLINE OF THE ROCK FORMATIONS. 

The rock formations of the Cripple Creek district may be divided into two very 
distinct groups. One comprises ancient crystalline rocks, which make up a great 
portion of the Colorado range and the plateau to the west and upon which Paleozoic 
and later sediments have been deposited. These rocks originally occupied the 
entire area of the district. 


t 


ANCIENT CRYSTALLINE ROCKS-GRANITE. 43 

Iii Tertiary time, as a part of the great eruptive activity manifested in this 
general regiori, a volcano broke through these fundamental rocks at about the center 
of the area. The products of this Cripple Creek volcano, together with a minor 
occurrence of a rock of about the same age, but having a different source, constitute 
the second group. 

ANCIENT CRYSTALLINE ROCKS. 

The rocks of the older division embrace granites, gneisses, and schists, and in 
addition a small area of olivine syenite and numerous dikes of diabase which cut 
the first three named above. All are probably of pre-Cambrian age. 

GRANITE. 

The granites of the district may be divided into a number of varieties, each 
distinctly recognizable in the field. They were described by Cross and named, 
respectively, Pikes Peak, Cripple Creek, and Spring Creek types. No attempt to 
separate them on the map was made by him. Dr. E. B. Mathews, who assisted 
Mr. Cross in the mapping of the Pikes Peak quadrangle, has made a somewhat 
detailed study of the granites within that area and has published his resuP: in the 
Journal of Geology, volume 8, 1900, pages 214-240. 

PIKES PEAK GRANITE. 

The Pikes Peak variety, the most extensively developed rock in the district, 
occurs to the north, east, and south of the area occupied by the volcanic rocks and 
for long distances in those directions beyond the limits of the region shown on the 
map. It is a light-pink to red coarse-grained rock, noticeably deficient in dark 
constituents, and much of it rather poor in quartz and hence consisting largely of 
an alkali feldspar which in some cases gives to it a porphyritic appearance through 
the development of more or less idiomorphic columnar individuals up to over an 
inch in length. Many of these large feldspar crystals are so arranged as to give to 
the granite a rather pronounced flow structure, and this drawn-out appearance is 
increased in many places by shearing. At some points, as on Calf Mountain, the 
shearing has been sufficient to transform the granite into a gneiss, with tails or 
schlieren of the quartz, feldspar, and mica fragments, and knots or augen of the 
feldspar phenocrysts. Not uncommonly even these traces of original texture are 
obliterated over small areas, and the equivalence of the resulting even-grained 
much foliated gneiss to the Pikes Peak granite is established only through marginal 
gradations into more massive rock. The extreme degree of foliation is reached 
alone: certain narrow zones where shearing has been so intense that a true schistose 
structure has been developed. Weathering causes a marked disintegration of the 
rock, furnishing a medium-grained angular gravel, composed either of separate 
mineral grains or of small fragments of the rock. This disintegration, with the 
formation of gravel, unquestionably has much to do with the even slopes of many 
of the granite hills. The massive rock is thus covered, and more advanced stages 
of decay are not often observed. 

Under the microscope microcline with its characteristic twinning is seen to be 
generally the most abundant constituent and is usually fairly fresh. Plagioclase 


44 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

is another important component and proves to be a sodic oligoclase. Beside the 
prevailing albite twinning lamellae arranged according to the pericline law are 
sometimes seen. The mineral is often turbid through kaolinization. Orthoelase 
is more variable in amount, from fairly abundant to rare, but is on the whole less 
common than plagioclase. Microperthite is plentiful in some specimens, while less 
regular intergrowths, resulting in uneven extinction, are occasionally found. 

Quartz, though present in varying amount, is exceeded in abundance only by 
microcline when the group as a whole is considered. It occurs in irregular grains, 
ranging in size from exceedingly small ones up to those several millimeters in 
diameter. It is not much cracked, gives simultaneous extinction, and is glassy, 
but contains countless small fluid inclusions arranged in intersecting lines or planes 
which appear to have no definite crystallographic direction, or are crowded in 
certain parts. Another class of inclusions consists of minute hair-like rods or 
needles, without definite arrangement and usually of dark color. A few of the 
largest are brown and very strongly refracting, and it is possible that they are all 
composed of rutile. Several small rounded grains of quartz with the same orien¬ 
tation are sometimes seen penetrating an individual of feldspar, and more typical 
micropegmatitic intergrowths occur as small patches giving arborescent figures in 
polarized light; sometimes the orientation of one of the constituents is similar to 
that of a near-by individual of the same mineral. A decrease in the amount of 
quartz may produce a syenitic facies of the granite, like that from the Ajax mine, 
an analysis of which is given on the next page. 

Biotite is the only ferromagnesian mineral present and is rarely abundant. 
It occurs in isolated plates or as clusters of irregular scales and is usually greenish 
brown in basal sections and yellowish parallel to the vertical axis. Chloritization 
is sometimes considerably advanced, producing a material ranging from strongly 
pleochroic to almost colorless. Locally, along with the chlorite, small granular 
particles of epidote and of black iron ore separate out along cleavage planes. The 
colored chlorite apparently contains much of the iron of the mica, for separation 
of iron oxide is a less common accompaniment of the green than of the colorless 
variety. 

Of the accessory minerals, apatite in the usual prismatic habit and magnetite 
in large and small grains are the most common. Zircon is at times comparatively 
abundant. In numerous instances it is dull and in reflected light appears whitish 
and opaque as if through decomposition. Here and there a fragment of titanite 
is present . Some of the small brownish crystalline particles included in the quartz 
appear to be referable to rutile, while prismatic or rounded grains of a different 
character of brown, noticeably pleochroic, correspond to allanite. Minute corroded 
fragments of biotite when cut somewhat inclined to the base are readily confused 
with the latter mineral. Flakes of hematite or limonite, probably secondary, are 
sometimes present in the quartz and feldspar. Near mineral-bearing fissures 
pyrite and occasionally fluorite and zinc blende are introduced and the feldspars 
are partially sericitized. 

With the exception of the gneissic structure sometimes developed as above 
mentioned, the texture of these rocks is typically granular. 


ANCIENT CRYSTALLINE ROCKS-GRANITE. 


45 


The chemical character of this type of granite is expressed in the following 
analyses, made by Doctor Hillebrand: 


Analyses of Pikes Peak granite. 


! i. 

II. 

! 1 . 

II. 


77.03 

66.20 

so 3 . 


None. 

M 203 . 

12.00 

14.33 

Cl. 


Trace. 


.76 

2.09 

F. 

.36 

(?) 

FeO. 

.86 

1.93 



.12 

MsO. 

.04 

.89 

MnO. 

Trace. 

.13 

CaO. 

.80 

1.39 

BaO. 

Trace. 

.18 

Na s O. 

3.21 

2.58 

SrO. 

None. 

Trace. 

K,0... 

4.92 

7.31 

Li 2 0. 

Trace. 

Trace. 

II 2 0-..'. 

.14 

.48 




H 2 0+. 

.30 

.83 


100.55 

99.74 

TiO •>...'. 

.13 

.65 

Less O for F. 

.15 

0. 

Zr0 2 . 


.02 


100.40 

99.74 

C0 2 . 


.36 




PjOi. 

Trace. 

.25 





I. Pikes Peak granite. Typical. Sentinel Point, western part of Pikes Peak massif. Jour. Geol., vol. 8, 1900, p. 237. 

II Pikes Peak granite. Local syenitic facies. Ajax mine, level 6. 

\ 

CRIPPLE CREEK GRANITE. 

Extending from the volcanic area westward beyond the mapped district is a 
light-red granite, which differs in texture from the Pikes Peak type and which has 
received the name Cripple Creek type. It is a medium, fairly even-grained rock, 
with an occasional feldspar (larger and more idiomorphic than the rest, causing a 
slight porphyritic appearance. Quartz is somewhat more abundant and more 
evenly distributed than in the Pikes Peak granite, and the same may be said ol 
mica. To this type is assigned the island-like mass of granite in the breccia on Bull 
and Ironclad hills. 

Concerning the correlation of the dikes and irregular masses of finer grained 
granite found cutting the Pikes Peak granite, there may be some doubt. Mathews 
refers some of them to the Cripple Creek type and some to a separate division which 
he calls the “fine-grained type.” But from such evidence as could be obtained 
both in the field and with the microscope, the smaller areas appear to be composed 
of a rock which corresponds closely with the Cripple Creek variety, and where it was 
possible to define their boundaries, they have been mapped as such. It is not 
unnatural that the smaller masses should in general have a finer grain than the 
large areas. The Cripple Creek granite has suffered much less shearing and deforma¬ 
tion than the Pikes Peak type. 

The results of the weathering of this rock contrast in some respects with those 
produced by that of the coarser grained variety. Instead of crumbling to angular 
gravel, this granite yields on disintegration subangular blocks of large and small 
size. This probably accounts for the apparent abundance of the dike granite in 
the Pikes Peak variety, fragments of the finer grained rock littering the surface of 
the coarser grained rock. On this account also the mode of alteration of the 


13001 — No. 54—06 - 5 














































46 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


Cripple Creek granite is more readily studied than in the Pikes Peak type. Biot it e 
loses more or less iron, which distributes itself through the partially kaolinized feld¬ 
spar and deepens the red color of the rock. Further change leaves the biotite 
conspicuous though lusterless and gives to the rock a dirty brownish-red color. 
Along phonolite dikes a common decomposition leaves the rock porous through 
removal of much of the quartz and mica. 

A microscopical examination of this rock confirms the conclusion that its 
composition is not very unlike that of the Pikes Peak variety. Microcline is probably 
the most plentiful constituent, and is usually comparatively fresh. In some 
instances, besides the usual crosshatching due to the combination of albite and 
pericline twinning, individuals are twinned according to the Carlsbad law. Occa¬ 
sionally a fine microperthitic intergrowth is present, and the mineral then becomes 
microcline-microperthite, but whether the other component is orthoclase or plagio- 
clase could not be determined. Orthoclase, the next abundant feldspar, is usually 
untwinned and more or less turbid through the development of kaolin and highly 
polarizing aggregates of muscovite flakes. Plagioclase is in general less common 
than in the Pikes Peak type, but is more variable in composition, having been found 
from albite to calcic oligoclase, inclusive. It is twinned polysynthetically and is 
usually turbid like the orthoclase. In a specimen from the Alpha tunnel the 
plagioclase appears to have been the earliest feldspar to crystallize; its grains are 
often corroded, but where inclosed in microcline, as is not uncommon, it has good 
form and the turbid interior is surrounded by an even, narrow border, perfectly 
clear and of slight ly higher extinction angle. A few grains of ordinary microperthite 
are present. Quartz occurs as usual in the granites, in irregular grains of varying 
size and showing inclusions similar to those in the Pikes Peak type. It is sometimes 
present as poikilitic grains in the microcline, and locally shows a tendency toward a 
definite intergrowth. Little patches of typical micropegmatite occur at places. 

The micas complete the list of essential constituents. Biotite, though seldom 
abundant, is the more common, occurring as brown or greenish-brown isolated plates 
of not very high birefringence. A frequent product of alteration is chlorite, often 
associated with epidote and black iron ore. Fully as common is a bleaching of the 
biotite and transformation into muscovite, a process which can be clearlv observed 
in some sections. Muscovite occurs in three ways—secondary from biotite, as just 
noted, secondary from feldspar, and primary. In the second case the aggregate 
sericitic mass resulting from the weathering of much of the feldspar seems to arrange 
itself into shreds and patches having similar orientation, thus producing grains of 
muscovite. In the last case clear muscovite, often corroded, comes up sharply 
against and sometimes penetrates perfectly Iresh biotite of different orientation; it 
also occurs between grains of other components. 

In addition to these principal constituents several minerals are present only in 
grains of microscopic size. Magnetite, apatite, zircon, and titanite occur in rapidly 
decreasing abundance. Small grains of tourmaline are sometimes seen, and show 
pleochroism in strong yellows, greenish brown, and blues. Prismatic crystals of 
brown color and marked pleochroism are more certainly referable to allanite than 
similar grains in the Pikes Peak variety. A few grains of rutile are present. 


ANCIENT CRYSTALLINE ROCKS-GRANITE. 


47 


Fluorite is present in sections from several localities and in a few instances 
appears to be primary, inclosing magnetite and tourmaline, penetrating individuals 
of quartz and occurring as sharp interstitial grains between perfectly fresh individ¬ 
uals of other minerals, and also included in feldspar. Cleavage is noticeable and the 
color ranges from colorless through pale pink to patches showing very deep purple. 
Traces of crystal form occasionally exist and minute fluid inclusions are sometimes 
observed. Although some fluorite, known to have been introduced into the granite 
through later fissures, occurs in much the same manner as above described, certain 
facts support the view that the mineral is in other cases an original constituent of the 
rock. Fluorine is known to occur in several minerals in the pegmatite veins which cut 
the granite of the peak. Moreover, Mathews’s descriptions of fluorite in the granites 
of the Pikes Peak quadrangle furnish almost convincing evidence as to its primary 
nature, and perhaps most conclusive of all is its distribution in remote and widely 
separated parts of the quadrangle, an area of nearly 1,000 square miles, and in locali¬ 
ties removed from vein mineralization. But it can be stated that within the limits 
of the Cripple Creek district primary fluorite is a rare constituent of the granites. 

Pyrite occurs in the granite near mineralized fissures, as in nearly all of the 
specimens from mine workings. Besides the epidote derived from the decomposition 
of biotite, this mineral sometimes occurs as faintly pleochroic aggregate patches 
scattered through the more decomposed rocks. Small areas of carbonate are occa¬ 
sionally seen, and hematite and limonite result from the weathering of magnetite. 

These rocks have the hypidiomorphic-granular texture of the typical granite. 

An interesting result of shearing of this granite is the production, along certain 
very narrow zones, of sericite and sillimanite. 

SPRING CREEK GRANITE. 

The Spring Creek type is not extensively developed, occurring only on the 
southwestern half of Red Mountain and on the hill to the south on the opposite 
side of Spring Creek. It is a bright-red, even-grained rock, containing conspicuous 
rounded grains of quartz 1 or 2 mm. in diameter. No specimen of very fresh 
material could be obtained. 

The color is found to be due to staining of the turbid feldspar grains with 
limonite. While orthoelase is probably the most abundant feldspar, the twinning 
of plagioclase is often seen, but further determination is impossible. Microcline 
is sparingly present and possibly a little microperthite. Quartz is abundant in 
clear grains which sometimes show related orientation when embedded in the feldspar. 
In a small dark fragment here and there and an occasional patch of secondary 
epidote, there is indication that a little biotite was originally present. Muscovite 
appears in the feldspar as small flakes, some of which have the same orientation 
and are parts of so-called skeleton crystals. Several small grains of fluorite were 
considered by Cross to be primary, but to the writer appear rather as of later age 
than the consolidation of the rock. 


RELATIVE AGE OF THE GRANITES. 


A 


Within the limits of the area mapped, little evidence as to the relative ages of 
the Pikes Peak and Cripple Creek granite is furnished by the contact of the two 


48 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


rocks in the southwestern part of the district. But from the smaller amount of 
shearing and deformation which the Cripple Creek type has undergone, and from 
the presence in the Pikes Peak granite of innumerable dikes of a granite which is 
almost without question assignable to the Cripple Creek variety, the Pikes Peak 
granite may undoubtedly be considered the older. This was the conclusion 
reached by Cross and Mathews in a much larger field. No evidence as to the 
relative age of the Spring Creek granite was obtained. 

PEGMATITE. 

Closely related to the granites is pegmatite, which forms innumerable dikes or 
veins in various parts of the district. They are rather common in the Pikes Peak 
granite and locally occur in the gneiss, but only rarely cut the Cripple Creek granite. 
It is believed that most if not all of the pegmatite veins were a late phase of the 
•eruption which produced the Cripple Creek granite, for in several places, notably 
along the Florence and Cripple Creek railroad south of Hollywood, typical well- 
defined veins of pegmatite seem to grade directly into dike granite similar in 
character to that of the main mass west of Cripple Creek. 

The dikes are usually narrow and of red color, being made up principally of a 
potash feldspar with considerable quartz and smaller amounts of muscovite and 
well-crystallized magnetite. Occasionally the proportion of quartz is much greater, 
and the dike then may be mistaken for a quartz vein. Prospecting at several 
places has revealed their barren nature. 

An examination under the microscope of one of the more “graphic” of these 
pegmatites reveals abundant microcline, all arranged with the same orientation. 
Quartz, present in about equal amount, penetrates the microcline granophyricallv. 
Muscovite, often- showing beautifully its skeleton structure, is less plentiful and lias 
different orientation in different individuals. A few grains of magnetite are also 
present. 

GNEISS. 

Pocks of granitic texture, showing marked foliation, but no distinct banding,® 
occur at numerous places in the district. They belong to several varieties, but 
because of small and indefinite extent all but two have been omitted from the 
map. Of these two, both have been given the same color, since the mass on 
Calf Mountain is small and its origin is not absolutely certain. 

WOMACK GNEISS. 

The typ.e of gneiss which has the greatest development underlies most of the 
town of Cripple Creek and forms the ridge to the northwest. It also extends as a 
band averaging a third of a mile wide from the slope of Gold Hill westward beyond 
the boundary of the area shown on the map. A mass of similar character occurs 
on the ridge northeast of Cameron and there meets the Pikes Peak granite, but 
the nature of the contact is not well shown and the mapping of the rocks at that 

a The rocks thus described do not fall under the definition recently brought forward by Van Hise, who applies the 
term gneiss to a banded rock the bands of which are petrographically unlike one another. (Mon. U. S. Geol. Survey, vol. 
47, 1904, p. 782.) 





ANCIENT CRYSTALLINE ROCKS-GNEISS. 


49 


place is approximate only. The rock takes its name from Womack Hill, which 
stands at the eastern edge of the town of Cripple Creek and whose western slope 
is made up of this gneiss. On the old map the rock was not distinguished, but 
was shown partly as granite and partly as schist. 

The origin of the Womack gneiss is not certainly known; it was probably 
derived by pressure from a granitic rock which, to judge from the small amount of 
quartz present in some places, may have been locally of syenitic or monzonitic 
character. There is no evidence that it is related to the Pikes Peak granite, and 
it is certainly older than the Cripple Creek granite, for it is frequently penetrated 
by narrow stringers and dike-like intrusions of the latter, as can be well seen in 
the various railroad cuts near the Short Line station and along the streets in the 
vicinity of the Warren School in Cripple Creek. It seems probable, therefore, 
that it has been derived from a third distinct granite, which, because of the greater 
deformation it has suffered, is thought to be older than either of the others. 

It is a rather dark, brownish-gray rock of medium grain and fairly uniform 
texture, carrying an abundance of red feldspar and deep-brown mica, and appar¬ 
ently not much quartz. It is characterized by a gneissic structure which varies 
from schistosity to a foliation so massive that the hand specimen shows almost no 
banding, and only larger exposures reveal the true foliated nature of the rock. 
Weathering changes the color to a dirty gray-brown, leaves the biotite conspicuous, 
and thereby exaggerates the schistose appearance. 

Under the microscope orthoclase is seen to be the most abundant feldspar. 
Plagioclase is next in importance and is albite or sodic oligoclase. It generally 
shows albite' and in some cases pericline twinning, but is occasionally untwinned. 
Microcline occurs in varying amounts, hut is seldom abundant. Quartz is found 
to be more plentiful than a megascopic examination would indicate. Inclusions 
are almost absent in some specimens, but in others they occur in profusion. As 
in the granites, they are fluid-filled cavities. Undulatory extinction is rather 
common. The feldspars often hold small oriented grains of quartz, while little 
patches of micropegmatite in arborescent patterns are not uncommon. Biotite 
is the prominent ferromagnesian silicate and occurs in irregular large and small 
plates, frequently corroded, and sometimes contorted. Pleochroism from light 
yellow to deep greenish brown is marked, and the absorption parallel to the cleavage 
is so great that many basal sections are practically opaque. The mineral doubtless 
holds a large percentage of iron. Chloritization is common and decomposition 
along the cleavages into epidote and magnetite is not infrequent. Muscovite 
occurs sparingly as an original constituent, and sometimes is clearly derived from 
biotite with the separation of iron oxide. Apatite is always present, and some¬ 
times is comparatively abundant. Titanite varies in amount, but is on the whole 
rather plentiful in very irregular grains. Crystals of zircon are by no means rare, 
and occasionally a minute prism of tourmaline and a small lath of primary epidote 
are seen. The most important accessory is magnetite, which frequently attains 
considerable prominence. In addition to the foregoing constituents, the gneiss 
northeast of Cameron contains abundant sillimanite. 


50 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

In the imdulous extinction of the quartz, the contortion of the mica, and 
sometimes distinct cataclastic structure, together with a rude arrangement of the 
constituents in parallel position and in bands, there is additional evidence of defor¬ 
mation. 

OTHER VARIETIES. 

Reddish to dark-gray gneissic rocks, usually of finer grain than the type just 
described, occur as streaks and patches within the Cripple Creek granite, particu¬ 
larly near the contact with the Womack gneiss. 

Biotite is the prominent constituent, though feldspar is plentiful, particularly in 
the less foliated types. In some cases there seems to be a direct gradation into the 
Cripple Creek granite, suggesting that they have been derived from it through shear¬ 
ing; but their lithological similarity to the Womack gneiss makes it probable that 
they are masses of that rock which have been caught up in the granite at the time of 
intrusion. The microscope shows that they are practically identical, as to mineral 
composition, with the Womack gneiss, except that orthoclase has been largely 
changed to microcline by the crushing which has taken place. 

Another variety of gneiss is that derived by shearing of the Pikes Peak granite. 
As mentioned in the description of that rock (p. 43), deformation has in some places 
been sufficient to produce an augen gneiss or even a still more foliated rock. Gneissic 
facies of this kind exist in the neighborhood of the contact with the Cripple Creek 
granite in the southwestern part of the district, on Beacon Hill and near the Thomp¬ 
son mine. Still greater shearing has produced a rock which is with difficulty recog¬ 
nized as having been derived from the Pikes Peak granite. All the large feldspar 
crystals have been destroyed and biotite appears to have been formed under the 
metamorphosing conditions that obtained. The resulting rock is a dark, micaceous, 
decidedly foliated gneiss. It occurs in several places as narrow zones, and in the 
southeastern part of the district is frequently encountered in small, ill-defined areas. 
A mass on the southern slope of Calf Mountain can be roughly outlined and, as has 
been stated, has been mapped with the Womack gneiss. The rock in that locality 
bears considerable resemblance to the Womack variety, of which it may possibly be 
an included fragment in the Pikes Peak granite. If that be the case, the Pikes 
Peak granite is certainly of later age than the gneiss. But marginal gradations into 
fairly massive granite and the occurrence of narrow strips of similar rock along 
near-by shear zones make it probable that the gneiss has been formed directly from 
the Pikes Peak granite. 

Related to the foregoing, and probably representing even more intense meta- 
morphism, are the narrow, dike-like zones of dark-colored foliated rock—for exam¬ 
ple, the so-called “schist vein” encountered in the Ajax mine and the similar occur¬ 
rence in the cut on the Low Line of the electric railway near the point where it passes 
under the Florence and Cripple Creek Railroad west of Victor. These are made up of 
clear, untwinned feldspar, a few grains of quartz, abundant green biotite, and con¬ 
siderable actinolite, with small amounts of apatite, sphene, and magnetite. Recrys¬ 
tallization has doubtless occurred, but crushing is evident not withstanding. 


ANCIENT CRYSTALLINE ROCKS-SCHIST. 


51 


SCHIST. 

The foliated rocks of granitic texture have been described in the preceding para¬ 
graphs as gneisses. Besides these, however, there occur in the district areas of 
decidedly foliated and cleavable rocks, the origin of which is not clear, but which can 
be easily mapped and are here described under the name of schist. More specifically, 
they are quartz-muscovite schists. The areas designated as schist on Cross’s map 
contain, besides the above rocks, several masses of what is in this report considered 
as gneiss. 

A microscopic examination would seem to indicate two different tjqres—one 
exceedingly schistose through the development of silvery or purplish muscovite in 
flakes up to a centimeter or more in breadth, the other more dense and massive, gray 
to nearly black, and apparently mica-free. But in reality these two types can not be 
separated; they grade into each other. The denser type is found carrying muscovite 
in increasing amount until it can not be distinguished from the more schistose. That 
this gradation is areal as well as constitutional can be seen in the schist mass north¬ 
east of the town of Cripple Creek, where the northwestern portion is chiefly of the 
denser type and the rock becomes more and more schistose toward the southeast. 

Rocks of this kind form a northwestward-trending belt about half a mile wide 
and 4 miles long, reaching from Cameron to the base of Red Mountain, interrupted, 
however, by areas of later volcanic rock. In a general way this belt separates the 
Pikes Peak granite on the northeast from the gneiss on the southwest. A smaller 
belt of like direction and similarly interrupted reaches from the western slope of Gold 
Hill to the foot of Mount Pisgah, and possibly beyond. This strip roughly marks the 
line between gneiss and Cripple Creek granite. An area of schist surrounded by 
breccia, near Fairview station, on the High Line, may represent a continuation of this 
belt. An uneven narrow band of schist of the same character as the foreg-oino- rocks 
follows the contact bet ween the Cripple Creek and Pikes Peak granites west of Beacon 
Hill. 

The microscope shows that all the rocks have a pronounced schistosity. Their 
most characteristic component is an aggregate mass of sericite, which shows by the 
parallel, almost fluidal arrangement of its minute shreds that the rocks have been 
much sheared. In the denser rocks sillimanite occurs very frequently with the seri¬ 
cite, in a similar way, forming bands, parallel to the schistosity, of small fibers and 
prisms. One or both of these minerals constitute a base or matrix in which are found 
individual grains of other constituents. Both are seen encroaching indiscriminately 
on all the other minerals, regardless of physical character or chemical composition. 

Quartz is often plentiful, occurring as lenses or augen, with numerous smaller 
grains forming tails at each end. In many specimens it is penetrated by needles of 
sillimanite and shreds of sericite, and in some it is in this way almost destroyed. 
Strain shadows and cracks are of common occurrence. A few small grains of 
fresh microcline are noticeable in one or two specimens. Turbid patches, many of 
them nearly destroyed by the advancing sericite, in some cases show albite twinning 
and extinctions corresponding to albite and oligoclase albite, while in others they 
show no twinning and are probably orthoclase. Careful examination by convergent 
polarized light reveals the presence of numerous clear grains of untwinned feldspar, 


52 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

probably for the most part orthoclase, with cleavage sometimes distinct . Muscovite 
is generally rather abundant, especially in the more foliated types, as irregular, ragged 
flakes which often appear to have resulted from recrystallization of the sericite 
base, while in several instances they are seen to have been derived from biotite. Bio- 
tite itself occurs in considerable amount in a few specimens and sparingly in some 
others, and at times gives evidence of its former abundance through the presence of 
pseudomorphie areas of sericite and strongly pleochroic chlorite, with the excess of 
iron separated out along the original cleavages as magnetite. 

In some of the darkest, least schistose rock from the area south of Red Mountain 
there occur, along with abundant sillimanite, numerous grains of a mineral which has 
been identified as corundum. It forms hexagonal prisms up to 1 mm. long and half 
as broad, terminated sometimes by the unit pyramid. Sometimes it forms hexago¬ 
nal plates 0.8 mm. across, and frequently it occurs in irregular grains. An imperfect 
rliombohedral cleavage is visible in some individuals. At times a patchy but dis¬ 
tinct pleochroism in blue is seen in parts of a crystal. The refractive index is notice¬ 
ably high. Isotropic sections give a uniaxial figure of negative character. The 
double refraction, as compared with that of other minerals in the section, appears 
somewhat higher than the recorded value for corundum, but owing to its excessive 
hardness the grains of this mineral are found to be considerably thicker than the rest of 
the slide, and as a result its interference colors are proportionally increased. Prisms 
and irregular grains, as well as ill-defined, radiating patches, of epidote are often 
observed. Apatite is common in some specimens, and not infrequently small parti¬ 
cles of zircon are seen. Both these minerals are present in broken or contorted 
grains. Magnetite is usually very plentiful in large and small grains, which at times 
take the form of octahedrons. 

Where feldspar and biotite are found sillimanite appears to be in process of 
formation, occurring in aggregates of very minute fibers radiating in all directions, 
with larger prisms in the interior of the mass. It appears to be an intermediate 
product in the process which finally results in the formation of the extremely 
schistose muscovite rocks. In such specimens, too, there are bands of quartz 
and feldspar grains which exhibit sometimes true granitic texture and at others 
typical cataclastic structure. 

Cross regarded the schists that he found in the course of his study of the Pikes 
Peak quadrangle as, for the most part, inclusions of exceedingly metamorphosed 
ancient sediments, but bethought that some, if not all, of these particular foliated 
rocks of the Cripple Creek district have been produced from Archean gneisses. A 
study of the occurrence of these rocks and of their character as revealed by the 
microscope would point to the same view, but chemical evidence obtained later 
makes it appear probable that the schists were not derived from granitic gneisses. 
The following partial analysis by W. T. Schaller of a representative muscovite schist 
suggests, rather, by the low silica and high alumina, potash, and water, a relation 
to the phyllites or clay slates. The material was collected near the mouth of the 
Cripple Creek and Gold Hill tunnel. 


ANCIENT CRYSTALLINE ROCKS-OLIVINE SYENITE. 


53 


Si0 2 .. 

ai 2 6 3 . 

Fe 2 0 3 

FeO.. 

MgO. 

CaO.. 

Na.O. 


Analysis of muscovite schist. 


. 51.88 

K 2 0. 

. 23.86 

Ti*0. 

. 7.24 

PoO- . 

. 1.89 

. 1.43 

. .21 
. .68 

Loss oil ignition.. 


5. 55 
.70 
.07 
6.05 


99.62 


OLIVINE SYENITE. 

A rock of considerable petrographic interest occurs on Iron Mountain, in the 
northwest corner of the district. It is just outside the boundary of the area shown 
in the first Cripple Creek map, and is not shown nor mentioned in the Pikes Peak folio. 
Only a portion of the mass is included within the area mapped in this report, and its 
southern and eastern limits are concealed by slide and alluvium. There is reason to 
believe that on the north a sharp contact exists with the Pikes Peak granite, which 
is probably the older. This rock in its most common development appears as a 
dark-brown or reddish-brown, rather coarse-grained aggregate of Carlsbad twins 
of feldspar, with smaller amounts of a black mineral with pyroxenic cleavage and a 
dark-brown mineral of rather vitreous luster and uneven fracture. 

The feldspar is almost exclusively microperthite—an intergrowth of orthoclase 
and albite—usually in Carlsbad twins, and commonly partially kaolinized. 
Quartz occurs very sparingly in irregular interstitial grains, which, nevertheless, 
sometimes show corrosion. Individuals of pyroxene up to half a centimeter in 
size exhibit at best only rude crystal form. The mineral is generally brownish 
yellow of varying intensities, but near the border frequently becomes greenish 
and sometimes deep green. Pleochroism is very slight, except in the green por¬ 
tions, and even there it is not marked. The angle of extinction is between 40° 
and 45°, but it was impossible to tell which one of the bisectrices lies nearest to 
the vertical axis. Cleavage is particularly good for pyroxene, and cross sections 
show, besides the prismatic, a pinacoidal cleavage sometimes of even better develop¬ 
ment. The second cleavage is probably parallel to the orthopinacoid, though 
this could not be determined with certainty. These properties and the character 
of the rock indicate that the mineral is diallage. It is more resistant to alteration 
than the other constituents. Olivine is present in almost the same amount as 
the pyroxene and in grains but little smaller. Good crystal faces are almost wholly 
lacking, but numerous individuals give a suggestion of the characteristic olivine 
outline. The mineral appears almost contemporaneous with the pyroxene, yet 
holds numerous crystals of apatite and grains of iron ore, which are uncommon 
in the bisilicate. The color ranges from a faint pink to a fairly strong but clear 
and transparent brown. The mineral is nearly isochroic. Besides the usual 
irregular cracks, two sets of cleavages are present, at right angles and of different 
degrees of perfection. The rough surface attests to the high index of refraction 
and the interference colors are less brilliant than usual because of the high double 
refraction of the mineral. The axial angle lies in the basal pinacoid, is smaller 
than for ordinary olivine—giving interference figures whose hyperbolas curve 















5 4 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


markedly—and is acutely bisected by the axis of least refraction. Alteration 
products are of several kinds. Very commonly the mineral is changed along 
cracks and cleavages to feathery serpentine which is of exceptionally strong color— 
deep bluish green—and noticeably pleochroic, probably because of richness in 
iron. The serpentine is not always confined to the olivine boundary, but often 
fills cracks and spaces throughout the rock. A less frequent decomposition produces 
pseudomorphic, mixed aggregates of limonite and chalcedonic silica, much as in 
the decomposition of iron-rich garnets. Still another product of alteration is a 
material of brownish-yellow color, forming scaly aggregates. When crystalliza¬ 
tion is more complete the mineral appears in good-sized foils showing intense 
pleochroism—strong brownish yellow across the cleavage and deep green or some¬ 
times brown parallel to it. The transformation from olivine is beautifully shown 
in some cases. This mineral has the cleavage, high double refraction, and charac¬ 
teristic surface of mica, which it is beyond cpiestion. Not uncommonly a chlorite 
of beautiful deep-blue color accompanies the mica. Occasionally the olivine is 
changed to talc and limonite. The brown color, distinct cleavage, comparatively 
small optical angle, negative character, and the nature of the alteration products 
all point to an olivine rich in iron, like hyalosiderite . a 

Apatite is very abundant in well-formed prisms of noticeable size. Black iron 
ore is likewise plentiful in large, irregular grains. A very little zircon is present in 
grains which reach a size of 3 mm. 

The combination of alkali feldspar, olivine, and diallage is unusual, and justifies 
the application of the name olivine syenite. Somewhat similar rocks have recently 
been found in Wisconsin.® This rock also resembles in some respects the perth- 
itophyres of Chrustschoff/' 

Of equal interest are the segregations which have taken place in this magma. 
In the southern half of the mass covered by it occur small inclosed areas, connected 
by gradual transitions with the main mass, where an increase in the amount of 
feldspar and a corresponding decrease in olivine give a pyroxene syenite with 
accessory olivine. In such cases the rock is red, usually of finer grain than the 
olivine syenite, and then sometimes porpliyritic through the development of a 
few large feldspar crystals. In a few cases the olivine nearly or quite disappears 
and the prominence of quartz becomes such that the rock is a pyroxene granite. 

Along the eastern edge, and particularly at the north end of the mass, the rock 
gradually becomes much darker in color—-almost black. Feldspar is less promi¬ 
nent than in the olivine svenite and is of green color. Olivine is more abundant, 
but in less characteristic macroscopic grains. Iron ore is very plentiful, and fre¬ 
quently apatite occurs in beautifully - sharp green needles up to half a millimeter 
in cross section. Occasional glistening flakes of mica are seen. In thin sections 
feldspar is found still to be the most important constituent. It belongs to the 
plagioclase series and ranges from oligoclase to labradorite inclusive, the most 
abundant variety being a sodic labradorite. Albite, Carlsbad, and pericline 
twinning are often beautifully exemplified. Diallage occurs as in the main rock, 
but has the purple or lavender tint indicative of appreciable titania content. 


oCf. Weidman, S., Jour. Geol., vol. 12, 1904, pp. 551-561. 
b Tschermaks Min. u. petrogr. Mittheilungen, vol. 9, 1888, p. 476. 







ANCIENT CRYSTALLINE ROCKS-ANORTHOSITE. 


55 


Twinning parallel to both the vertical pinacoids is sometimes seen. The olivine, 
strangely enough, appears to contain less iron than that previously described. 
It is nearly colorless and the cleavage is less perfect. Its decomposition products 
are practically the same, however, and it is still rich in iron. Both pyroxene and 
olivine possess better crystallographic form than in the foregoing rocks. Black 
iron ore and apatite are especially abundant. Large and small grains of beautiful 
deep-red mica are associated with the ore. This facies is an olivine gabbro. 

At the northern limit of the mass the rock is much finer grained, and a sharp 
line between it and the Pikes Peak granite suggests that it is a contact facies. 
Feldspar is abundant in imperfect laths, but is not so plentiful as above. It cor¬ 
responds to the composition Ab 3 An 4 . Diallage is very common in irregular grains. 
It is still more deeply colored than that just described and exhibits a slight pleo- 
chroism in lavender and brown. Besides the titanic oxide thus contained, it is 
frequently filled with several definitely arranged series of minute dark needles, 
doubtless of rutile, the so-called sagenite. Olivine was originally present in large 
amount, but is now wholly altered into the products already mentioned. The 
red mica is rather plentiful, and, as before, always occurs near the abundant iron 
ore, which is probabty titaniferous. Apatite is common, but less so than farther 
from the contact. The texture is granular and rudely ophitic. 

Beginning at the contact and passing to the inclosed segregations one encount¬ 
ers (1) the doleritic contact facies of olivine gabbro, (2) olivine gabbro, (3) olivine 
syenite—the principal rock of the mass, (4) pyroxene syenite, with accessory 
olivine, (5) pyroxene granite. 

This intrusion thus presents a very typical example of magmatic differentiation. 

ANORTHOSITE. 

Closely related to the olivine syenite is a rock which occurs in it as a dike 
10 to 20 feet wide, just inside its contact with the granite. This rock is not par¬ 
ticularly conspicuous, although detached pieces appear on the surface, but it has 
been exposed in several prospect holes. It is nearly white and is composed of 
individuals of plagioclase up to 10 cm. across, which show cleavage and excellent 
albite twin lamellae more than a millimeter thick. The freshest grains have a 
darker-colored, bluish interior and suggest labradorite. A few small grains of 
dark minerals are present between the feldspar individuals. 

The material is too decomposed to permit a determination of the exact char¬ 
acter of the feldspar, but the decomposition products, zoisite and epidote, occurring 
side by side, indicate that it holds considerable lime, and it is probably a calcic 
labradorite. Sericite also results in considerable abundance from the decompo¬ 
sition of feldspar. Small scattered grains of diallage have the same character as 
that in the olivine gabbro. A few fragments of the red mica are also seen. The 
original presence of olivine can not be affirmed, but patches made up of serpentine, 
limonite, and talc (?) probably result from the decomposition of that mineral. 

This anorthosite dike is thus seen to have a mineral composition such that it 
must be considered as belonging to the olivine-syenite group. It is, in fact, an 
extreme facies of the olivine-syenite magma. 


56 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

DIABASE. 

Numerous dikes and small masses of finely granular, dark rocks cut the gran¬ 
ites, gneisses, and schists, but are not intrusive into the later volcanic rocks of the 
district. This difference serves to distinguish them from the basaltic rocks of 
somewhat similar appearance which occur principally in the younger volcanics. 
These older rocks are usually decomposed at the surface into a greenish mass with 
characteristic concentric disintegration, but at no great depth fairly fresh rock 
is usually encountered. They occur principally in and northwest of the town of 
Cripple Creek and along the northern slopes of Brind and Straub mountains. 
Cross assigned them to the Algonkian or early Cambrian. 

Feldspar is developed in laths parallel to the brachy-axis which are frequently 
twinned according to the Carlsbad and pericline laws, in addition to the common 
albite twinning. It is usually turbid through kaolinization. The composition of 
the greater part corresponds to calcic labradorite, but in several instances there 
occur narrow outer zones of a clearer, more alkalic variety, which is sometimes 
even ortlioclase. Pyroxene is present in considerable amount and seems to be 
diallage. It usually shows a slight pleochroism in purple, and doubtless carries a 
small percentage of titanium. A common decomposition product is a brownish- 
green fibrous amphibole corresponding to uralite. In other cases the pyroxene 
alters into a brownish-yellow aggregate of micaceous aspect. Olivine itself was 
not seen, but the freshest specimens hold patches of secondary material, built of 
fibers arranged in the characteristic net-like manner and possessing the outline of 
olivine. This secondary material is yellow or brown, somewhat pleochroic, and 
gives high polarization colors like those of muscovite. Carbonates and a little 
serpentine are also present in some of these areas. Numerous grains of deep 
reddish-brown biotite of strong pleochroism, or in a few cases ordinary brown 
biotite, occur in irregular flakes. Apatite and magnetite are usually plentiful as 
accessories, the latter mineral often being present in the grill-like skeleton crystals 
frequently seen in rocks of this character. Carbonates, sericite, and abundant 
epidote and limonite are formed on the decomposition of these rocks. . 

The laths of feldspar are arranged among the other constituents in the man¬ 
ner known as the opliitic texture, which is characteristic of the dolerites or diabases. 

It is apparent that these rocks possess many resemblances to the doleritic 
contact facies of the olivine-syenite mass. The character of both monoclinic and 
triclinic feldspar and of the pyroxene and the presence of olivine and red mica 
relate the two rocks very closely and make it probable that many if not all of the 
diabase dikes of the Cripple Creek district are connected with the olivine-syenite 
intrusion. One or two dikes which contain ordinary biotite and in which olivine 
was not detected may be of different age. 

TERTIARY VOLCANIC ROCKS. 

The younger group comprises mainly the rocks of the Cripple Creek volcano. 
These are phonolite, leucitophyre (?), latite-phonolite, trachyte, syenite, trachydo- 
lerite, vogesite, monchiquite, and volcanic breccia. In this group is also included 
an areally unimportant occurrence of rhyolite, which had a different source, but 


TERTIARY VOLCANIC ROCKS-PHONOLITE. 57 

belonged to the same general period of Tertiary time as the rocks of the Cripple 
Creek volcano. 

To one acquainted with the work of Cross it is at once apparent that the pres¬ 
ent nomenclature of this group differs from that adopted by him. His names for 
the rocks of the Cripple Creek volcano were phonolite, trachytic phonolite, syenite 
porphyry, biotite andesite, pyroxene andesite, nepheline syenite, and basalt, the 
latter including plagioclase basalt and nepheline basalt. This difference arises 
from different conceptions of the characters of the rocks rather than from unlike 
definitions of the rock names. While this difference of views will be dealt with 
under each rock type recognized in the present report, a general comparison of the 
names used in the two papers is given at this place. 

The phonolite of Cross corresponds exactly to the phonolite of this report, with 
the one exception that the mass occurring on the summit of Bull Cliff was thought 
by him to be a peculiar phase of phonolite, while further studj^ shows it to be a 
trachydolerite. The trachytic phonolite, syenite porphyry, and pyroxene andesite 
established by Cross have been found impossible of separation, and are here named 
latite-phonolite. Microscopic and chemical examination of the rock formerly 
named biotite andesite show that it is a biotite trachyte, but is closety related 
to latite-phonolite. Nepheline has not been found in the granular rocks called 
nepheline syenite by Cross, and they are now described simply as sj^enite. Study 
of fresher representatives of the basic dike rocks than those collected by Cross indi¬ 
cates that they fall into three groups, namely, a second type of trachydolerite 
corresponding to his plagioclase basalt, monchiquite corresponding to his nepheline 
basalt, and vogesite, a rock probably not seen by him. The breccia, of course, is 
the same in both cases, though, as will be shown, there is a divergence of opinion 
concerning its composition. 

PHONOLITE. 

GENERAL DESCRIPTION.® 

Definition .—The phonolites are in general dense, fine-grained, porphyritic rocks 
of medium light to dark color, characterized by a large amount of alkalies, particu¬ 
larly soda, and considerable alumina, together with low bivalent bases and insuffi¬ 
cient silica to form free quartz or to combine with all of the abundant alumina and 
alkalies in the ratio of feldspar. The essential mineral composition of phonolite is 
in consequence alkali feldspar, nepheline, and an alkali pyroxene which usually con¬ 
tains ferric iron. Phonolite is a rare type of rock in the United States. 

Occurrence .—Rocks of this description occur in the Cripple Creek district as 
large and small bodies in and about the central volcanic area. The larger masses 
represent irregular intrusions from isolated local vents, and now, because of their 
greater resistance to degradation, form the summits of several of the Cripple Creek 
hills. As indicated on the map, phonolite occurs on Trachyte, Rhyolite, and Cop¬ 
per mountains, to the north, and on Big Bull and Straub mountains and Grouse 
Hill, in the southern part of the district. It also forms the crests of the hill east of 
Cameron, the hill east of Victor Pass, Beacon Hill, and the ridge west of the town 

a A comprehensive and detailed description of these phonolites was given by Cross, General geology of the Cripple 
Creek district, Colorado: Sixteenth Ann. Rept. U. S. Geol. Survey, pt. 2, 1S95, pp. 25-41. 



58 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

of Cripple Creek. The smaller bodies are sometimes also of irregular outline, as on 
the ridge west of Cripple Creek Gulch, but usually appear in definite sheetlike 
forms or dikes. They are abundant in both the volcanic rocks and the outlying 
granite, and exhibit a rude radial arrangement about the main eruptive center. 

Outside the mapped area also the rock occurs at various points within a radius 
of over 7 miles from the summit of Bidl Hill. Besides numerous dikes in the gran¬ 
ite, masses of notable size form the summits of Nipple Mountain, Miter Peak, Little 
Pisgah Peak, the hills south of Straub Mountain, the hill east of High Park, Mount 
Pisgah, and Cow Mountain. Phonolite is also exposed in several places on the 
southwestern slope of Pikes Peak to an altitude of 1 ] ,000 feet. 

Eruptions of phonolite took place at several different times. This rock fur¬ 
nished part of the material of the volcanic breccia and later invaded it as dikes. 
In the granite dikes may be found of at least two ages, and the larger intrusive 
masses may represent still another eruption. 

Appearance .—In a few places outside the district proper these rocks have a 
marked porphyritic texture. In general, however, they are almost aphanitic, with 
only occasional phenocrysts of glassy feldspar up to 1 cm. in size, or of pyroxene 
in small dark needles, or crystals of one of the sodalite group of minerals. When 
fresh they are usually dense and dark gray or greenish, with often a dull greasy 
appearance. Most of them have a platy structure or fissility, which often aids in 
distinguishing them from other varieties, and which in some cases, particularly in 
narrow 7 dikes, becomes pronounced. 

With the exception of the Beacon Ilill mass, which is considerably altered, the 
larger bodies are comparatively fresh. Pew of the dikes, however, are unaffected 
at the surface by the atmospheric agencies. Decomposition effects a bleaching and 
exaggerates the fissility. Incipient weathering causes the rocks to assume a gray¬ 
ish color, and on more complete change they become light yellow" or greenish yellow, 
or at times reddish. Oxide of manganese sometimes imparts to much decomposed 
rocks a brown color distributed either throughout their mass or as a coating along 
cracks and joints. 

Of this prevailing appearance there are one or two noticeable modifications. 
Some of the rocks are mottled by small lighter-colored spots or blotches, usually 
drawn out in the direction of the fissility, and probably caused by a slight decom¬ 
position of the feldspar microlites in those places. In other cases the mottling is 
due to small dendritic patches rich in segirine needles. Textural modifications are 
of two kinds. The most fissile rocks frequently contain small narrow druses, and 
in these cavities sharp trapezohedral crystals of colorless or yellowish analcite may 
often be seen. The second modification, which frequently accompanies the first, 
is caused by the development of megascopic nephelines. This mineral then occurs 
in stout hexagonal columns up to 2 mm. in size, possesses the usual oily luster, and 
is commonly red. Phonolites of this type occur on the w-estern slope of Khyolite 
Mountain, on the hill w^est of the town of Cripple Creek, and on Grouse Hill and 
Straub Mountain. When they weather, nepheline is one of the first constituents to 
be attacked and is readily removed, giving to the resulting mass a characteristic 
pitted surface. 


TERTIARY VOLCANIC ROCKS-PHONOLITE. 


59 


MINER A LOGICAL CHARACTER. 

The characteristic mineral constituents of these phonolites are alkali feldspar, 
nepheline, sodalite, nosean, analcite, aegirine, and aegirine-augite. As accessory 
minerals occur titanite, apatite, magnetite, and occasionally small amounts of a 
blue amphibole, biotite, and zircon. Olivine occurs very sparingly in one rock. 
A few minerals are present in grains so small as to be indeterminable 

Feldspar .—The feldspars are limited to the potash-soda varieties. In fresh 
rocks the phenocrysts are clear and glassy. They are usually tabular parallel to 
well-developed clinopinacoidal faces. Other crystallographic boundaries are in 
general only poorly defined, though occasionally smooth faces parallel to the base 
and, still less commonly, good orthopinacoids are seen. Intersecting cleavages are 
nearly always apparent, the basal being a little more prominent than the clinopin¬ 
acoidal. Carlsbad twinning is prevalent and in one rock mass the Baveno law also 
is exemplified. No indication of polysynthetic twinning nor of microperthitic 
intergrowth was observed. The feldspars of the groundmass present two definite 
habits, with probably all gradations between. In some rocks they are typically 
microlitic, being developed in rude laths parallel to the edge 010:001. Cross sections 
are nearly equidimensional, but as in the phenocrysts the clinopinacoid is more per¬ 
fect than the base. Carlsbad twinning is almost universal and a transverse parting, 
probably parallel to an orthodome, is often observed. In other rocks, and at times 
even in parts of the same section with the microlitic feldspars, the groundmass is a 
granular aggregate of feldspar grains which utterly lack definite crystallographic faces. 

Both the porphyritic and the groundmass feldspars are, so far as observed, 
monoclinic. Although Cross mentions the presence of anorthoclase, no indication 
of triclinic character could be detected. Sections from the orthodiagonal zone 
exhibit cleavages at right angles, with extinction parallel. In sections from this 
zone which are cut perpendicular to a bisectrix, it is ascertained that the axial plane 
is in the usual position—at right angles to the clinopinacoid—that the ortho-axis 
is the bisectrix of least elasticity, and that the feldspar is optically negative. Sec¬ 
tions parallel to the clinopinacoid show the perpendicular emergence of c, and a 
maximum extinction angle relative to the trace of the basal cleavage of about +9°. 
The maximum double refraction is always low and the refractive index is notice¬ 
ably lower than that of Canada balsam. These feldspars then appear to be entireh' 
homogeneous and monosymmetric. The relatively high extinction angle in clino¬ 
pinacoidal sections may be attributed to normal isomorphous replacement of pot¬ 
ash by soda. The feldspars of these rocks may therefore be called soda-orthoclase.° 

The most abundant product of l^drometamorphism of the phonolite feldspars 
is kaolin, probably accompanied by a little finely divided silica. The groundmass 
feldspars are frequently less kaolinized near individuals of segirine than elsewhere. 
In certain rocks, however, some of the phenocrysts have been partially changed 
into a colorless isotropic material, of lower index than the feldspar, which is prob¬ 
ably analcite. This alteration is not seen in very much decomposed rocks. The 
analcite almost always occurs in patches within the feldspar crystal, and the process 
by which it is formed is not revealed. Close to mineral veins the feldspars are 
partially changed to sericite. 


aCf. Pirsson, L. V., Am. Jour. Sci., 3d ser., vol. 47, 1894, p. 342. 





PLATE VII. 

» • 

Photomicrographs of Phonolite. 

A, Pkonolite (456 C- C.) from northern slope of Big Bull Mountain. Composed of soda-orthoclase, nephe- 

line, nosean, sodalite, analcite, and segirine. Characteristic texture due to abundance of nepheline. 
Veinlet crossing the plate is filled with analcite. .Egirine in small needles is particularly abundant 
near the veinlet. Magnified 28 diameters. 

B, Phonolite (209 C. C.) from summit of hill northeast of Cameron. Ragged individuals of aegirine inclosing 

prisms of nepheline and surrounding cores of segirine-augite. Magnified 28 diameters. 

C, Phonolite (455 C. C.) from hill east of Bull Cliff. Trachytic flow texture of groundmass and phenocrysts 

of soda-orthoclase and a?girine-augite. In the upper left-hand corner of the plate are crystals of 
nepheline inclosed by analcite. Magnified 28 diameters. 

D, Phonolite (251 C. C.), 2,000 feet N. 30° E. of Copper Mountain. Nepheline (A r ) somewhat turbid through 

decomposition, and aegirine (£) inclosed in a large individual of primary analcite (M). Holes in 
the section are indicated by II. Magnified 28 diameters. 

60 


U. S. GEOLOGICAL SURVEY 


PROFESSIONAL PAPER NO. 54 PL. VII 



A 


B 






C 


D 


PHOTOMICROGRAPHS OF PHONOLITE. 

















TERTIARY VOLCANIC ROCKS-PHONOLITE. 


(51 


Nei)heline.—T\\e distinctive mineral of these rocks, as of phonolites in general, 
is nepheline. It is a common constituent of every section studied and in several 
rocks makes up a large amount of the whole. It almost invariably exhibits auto- 
morphic development and occurs in the usual habit of hexagonal prisms bounded 
by basal planes. These crystals vary in size from 2 mm. down to a few thousandths 
of a millimeter. Their distribution through the rock is usually fairly uniform. 
The large crystals are naturally less abundant than the small ones. Nepheline 
appears to have cyrstallized at different times in different rocks. In some it is 
older than the feldspar and aegirine phenocrysts and was formed when the ground- 
mass was stifl fluid. In other rocks it is limited wholly to the groundmass, where it 
occurs with and between the feldspar microlites. In the majority of cases, no 
matter how small its crystals, it is older than the aegirine phenocrysts and occurs 
thus as abundant minute inclusions in the pyroxene. Occasionally the nepheline 
incloses small needles of aegirine and blue amphibole. Particularly noticeable is 
the partial or complete surrounding of nepheline crystals b} T analcite, while at times 
the two minerals are mutually allotriomorphic. 

In addition to its usual morphological and optical characters, the presence of 
nepheline is frequently indicated by the rock texture. Minute needles and inter¬ 
stitial grains of aegirine are commonly abundant in the groundmass, but seldom 
penetrate the nepheline, and the resulting numerous clear spaces, usually of rectan¬ 
gular outline, are often striking. Many of the larger nepheline crystals inclose 
numerous small flakes or scales of limonite or hematite, and this is doubtless the 
cause of their red color when viewed megascopically. 

A peculiar feature of some of the nepheline of these rocks is its behavior 
between crossed nieols. In some rocks a part of the nepheline, frequently a portion 
of a definite crystal, appears in polarized light as an aggregate of irregular elongated 
grains having indistinct boundaries, resembling almost exactly the subtrachytic 
groundmass, of which it frequently seems to form a part. This appearance is most 
noticeable in the larger individuals, but on careful observation it is found to be a 
property of much of the nepheline. Intergrowth of nepheline and feldspar is at 
once suggested, but the refractive index seems to be absolutely uniform through¬ 
out the crystal. This reason and also the freshness of the nepheline in parts so 
affected exclude the possibility of alteration products as the cause. The only 
other plausible explanation of the phenomenon is that the nepheline is optically 
anomalous. 

The common alteration products of this mineral are zeolites. They occur as 
small granular aggregates or as radially arranged fibers and cause the nepheline to 
become turbid. Their refractive index is low and they polarize more or less faintly, 
but in no case was their exact character determinable. Stilbite is probably one of 
these products. Cancrinite was not identified. In much-weathered rocks nephe¬ 
line may be completely removed. Sericite sometimes develops as pseudomorphs 
after nepheline near the walls of mineral veins, often before the feldspars show any 
sign of alteration. 

Sodalite and nosean .—Both chlorine-bearing and sulphuric anhydride bearing 
members of the sodalite group are important constituents of these phonolites. 

13001— No. 54—06-6 



62 GEOLOGY ANT) GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

Owing to their similar properties and development they are not readily distinguish¬ 
able. But careful study under the microscope, in connection with a consideration 
of the chemical analyses, leads to certain conclusions, which accord with micro- 
chemical tests performed by Cross. The variety bearing sulphuric anhydride is 
principally nosean, though an occasional decomposed crystal incloses a small grain 
of calcite when the remainder of the rock is almost carbonate free, and this may 
indicate the presence of hauyne. It occurs in clear-cut dodecahedral crystals from 
0.1 to 2 mm. in size and often has a pale-bluish or greenish color, particularly when 
inclosed in feldspar. It is characterized by exceedingly small, dark inclusions 
arranged in two or more series of definite, parallel lines. These inclusions tend to 
be most numerous near the periphery of the crystal and sometimes fail entirely in 
the interior. At times, however, they are so abundant throughout that the mineral 
becomes almost opaque. Embayments due to corrosion are frequently observed. 
Sodalite is on the whole considerabty more abundant than nosean and is sometimes 
a prominent constituent. It also occurs in dodecahedrons, but fully as commonly 
in forms which give square or elongated rectangular sections. Occasionally the 
crystals attain the size of the largest nosean individuals, but usually they are mucn 
smaller, sinking to less than 0.001 mm. in dimension. Regular gradation in size 
aids in making certain the identification of the smallest particles. The crystals 
usually show a clear outer border surrounding a dull-brownish interior whose color 
is probably due to inclusions. 

These two minerals were among the very first to crystallize from the phonolite 
magma and in consequence occur as inclusions in all the other important constitu¬ 
ents, though they are not common in nepheline. They lose their isotropic character 
, on weathering and are transformed into a faintly polarizing aggregate of, probably, 

a zeolitic. mineral. Sericite forms occasionally. 

*/ 

Analcite. —Lindgren a was the first to regard analcite as a primary constituent 
of igneous rocks, and with that view numerous later observers have concurred. 
Cross considered the analcite of the Cripple Creek plionolites to be primary, and 
this seems the only possible conclusion. Beside its occurrence in the drusy cavities 
as already described, this mineral is seen in irregular masses up to 1 mm. in size, 
which suggest filled cavities. In such places it is apt to be intimately associated 
with sharp, fresh crystals of nepheline and of tegirine. It also occurs in even the 
densest rocks as small veinlets, and here too legirine is unusually abundant. In a 
few instances, as already remarked, it appears to have crystallized at about the 
same time as the nepheline, but it is generally seen to have been the last product to 
solidify. These rocks seem to have crystallized under pressure sufficient to retain 
water in the magma, and Cross concludes 5 that the analcite formed “when the 
excluded water contents of the magma had been concentrated by a kind of differen¬ 
tiation, in spots or along certain planes.” Soda also appears to be concentrated 
in these places, as shown by the development of large nephelines and the especial 
purity and abundance of the aegirine. On account of the chemical composition of 
these parts of the magma, it appears that on holocrystalline development analcite 
is practically the only mineral known to exist in igneous rocks which could utilize 
the water and excessive soda. 


a Tenth Census, vol. 15, 1886, pp. 727-729; Proc. California Acad. Sci., 2d ser., vol. 3, pp. 51-57. 

b General geology of the Cripple Creek district, Colorado: Sixteenth Ann. Rept. U. S. Geol. Survey, pt. 2, 1895, p. 36. 







TERTIARY VOLCANIC ROCKS-PHONOLITE. 63 

The analcite is always clear, frequently shows distinct cleavages at right angles, 
possesses the rough surface clue to very low refractive power, and is practically 
isotropic, but frequently shows irregular patterns of the faintest polarization. 

JEgirine and segirine-augite .—These pyroxenie minerals are the only dark 
silicates of importance in the plionolites. zEgirine is the more abundant and is 
frequently present alone. It is purest and best developed where inclosed in analcite 
and there appears as narrow prismatic laths that are flatly tabular parallel to the 
orthopinacoid and terminated by low dome faces. Very small prism and clino- 
pinacoidal faces may occasionally be seen in cross sections. The mineral occurs 
in varying amount in different rocks. It ranges in size from prismatic phenocrysts 
several millimeters long down to the most minute needles and irregular grains in 
the interstices of the groundmass. A common mode of occurrence is "as a grain 
elongated parallel to the prism, full of included nepbeline and feldspar crystals, and 
with an outer zone which reaches out among the adjacent mineral grains as an 
oriented cement. It is frequently the case that the growth beyond the compara¬ 
tively solid core is mainly on the ends. Sheaf-like bundles of curving and forking 
gegirine needles occur in some rocks, usually in the denser varieties, and the forms 
assumed are sometimes very delicate.”® iEgirine laths are frequently seen wrapped 
around crystals of nepheline. Grains of magnetite are often the cores of segirine indi¬ 
viduals. Numerous irregular, disconnected grains, having similar optical orienta- 
iton over a considerable distance, occur in lines or planes through the rock and along 
both sides of analcite veinlets. The optical properties are as usual for the species. 
The angle lt:c is about 5°. The plechroism is intense: a = blue green, h = green, 
jC = greenish yellow to bright yellow, and a > b > c. Double refraction is high. 
The ends of some of the purer prisms sometimes show the brilliant yellows of 
acmite, and at times that variety occurs alone. 

The combination of this soda-iron molecule in an augitic pyroxene is rather 
common. The resulting segirine-augite occurs most frequently as solid cores to a 
surrounding mantle of segirine. From the center outward the properties grade 
progressively from those of pale green, almost isochroic augite with extinction angle 
a:c of over 40°, to those of pure segirine. The segirine habit appears to dominate 
the crystals, although clinopinacoids are more developed than in segirine. . 

The principal recognizable product of the alteration of these minerals is limonite. 
Carbonates sometimes result from the segirine-augite. 

Blue amphibole .—A blue mineral was observed by Cross in some of the phono- 
lites and considered by him to be probably a soda-lime amphibole. Material 
recently collected shows the mineral with better development than in the specimens 
that he studied. It occurs mainly in stout prisms, usually much smaller than the 
maximum size of 0.1 mm. Cross sections have characteristic amphibole outline, 
bounded by prisms and prominent clinopinacoid faces, and occasionally narrow 
orthopinacoids. A section approximately at right angles to c gave a prism angle 
of 123° 40'. Prismatic cleavage is present as usual, but is less perfect than in com¬ 
moner varieties and often can not be seen in the prism zone. In many cases 
the crystals have definite terminal planes consisting of the base, which makes an 

a Cross, W., op. cit., p. 28. 


t 







64 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

angle of ±73° with the vertical axis, and a negative orthodome which is less promi¬ 
nent and somewhat steeper. Low clinodomes are sometimes present, and in a few 
instances a negative orthodome is seen which is approximately perpendicular to 
the vertical axis. 

Cross sections show that the axial plane occupies the normal position, in the 
plane of symmetry, and that one of the optic axes lies very near to the vertical 
axis. The maximum extinction angle observed was a:c=+43° 30', a lying in 
the obtuse angle The optical angle is therefore large, but the axis of greatest 
elasticity may bisect it acutely. Pleochroism is marked, as follows: a = deep 
grayish or greenish blue, b = dull olive, with sometimes a tinge of purple, c = light 
yellow or greenish yellow. a>b>c, absorption along a and b being nearly 
equal. The index of refraction could not be determined definitely, but is about 
1.65 to 1.70. The double refraction probably never exceeds 0.025. Axial disper¬ 
sion is noticeable, but its character was not determined. The foregoing descrip¬ 
tion applies to what seem to be the most distinctive and characteristic sections.- 
The mineral appears to vary in composition, however, and in some sections the 
angle of extinction ranges from 20° at the periphery to over 40° at the center. 
Other well-formed crystals show uniform extinction a:c = about 25°. In such 
sections the absorption colors are a little lighter and of slightly different character, 
a = grayish blue, b = dull olive, c = light yellow. This last variety corresponds to 
the description given by Cross. 

Its association throws considerable light on the chemical character of this 
mineral. It frequently occurs, like aegirine, as ragged patches filled with inclusions 
of nepheline and feldspar. At other times it is a more or less fibrous aggregate. 
It sometimes surrounds, sometimes is surrounded by individuals of aegirine. 
Minute poikilitic grains of aegirine are abundant, and in numerous cases a definite 
micropegmatitic inclosure of aegirine may be observed. It appears, therefore, 
almost beyond question, that this amphibole is chemically related to aegirine. 

So far as known no one species yet described corresponds to this mineral. 
Its properties suggest a combination of two amphibole molecules analogous to 
aegirine-augite. Crocidolite is similar in some respects, but arfvedsonite agrees 
most closely, particularly with the variety of lower extinction, and may easily be 
one of the combining molecules, while the other one is unknown. 

Oilier minerals .—Titanite occurs in the small lozenges or the lath-sliaped 
forms it often assumes in phonolites. It is brown, shows strong absorption, 
and is often twinned parallel to the orthopinacoid (100). Apatite forms small 
hexagonal prisms and needles. A little magnetite is present in small grains, 
which often approach octahedrons. In some cases a grain of magnetite is inclosed 
at the center of an aegirine individual. A few foils of brown biotite of strong 
absorption occur in part of the Trachyte Mountain mass. Very small grains or 
rounded crystals of zircon may be seen in several rocks. Scattering grains of olivine, 
apparently as inclusions, and now showing resorption, occur in a rock collected by 
Cross from Rhyolite Mountain. 

In several of the Cripple Creek phonolites is found a mineral whose identity 
is not certain. It has a development and distribution similar to aegirine, from 
which it is not always to be distinguished. ‘‘It occurs in minute needles, colorless 


TERTIARY VOLCANIC ROCKS-PHONOLITE. 


65 


or pale yellowish, isolated or grouped in loose bundles. * * * The needles 

reach a length of 0.1 mm. by an average diameter of but 0.015 mm. * * * In 

certain needles extinction takes place parallel to the prismatic axis, and in such 
cases there is no definite dichroism. In other needles there is an oblique extinction 
and here there is a strong, clear yellow color for the axis nearly normal to the 
prism, while that near c is colorless, as before.”® The mineral is therefore 
probably monoclinic, but owing to absence of definite cross sections in the slides 
examined its optical orientation can not be determined. Cross regarded the min¬ 
eral as probably lavenite, and the unfailing presence of zirconia seems to support 
this view, for zircon does not seem to be sufficiently abundant to account for the 
amount of that oxide found. The weak pleochroism, however, and the impossi¬ 
bility of securing reliable data make any conclusion open to question. 

Two additional minerals of uncertain identity occur in almost the same manner. 
They are sparsely scattered through the groundmass and resemble the irregular 
grains and patches of interstitial aegirine. Both are colorless in the minute grains 
seen, and in both the refractive power is noticeably high. One has moderate 
double refraction and extinction, sometimes parallel and at other times over 40°. 
Its properties suggest a pyroxene, but in its mode of occurrence it does not cor¬ 
respond to that mineral. The other mineral has a similar arrangement of elasticity 
axes, but the double refraction is high. Except for the oblique extinction it resem¬ 
bles zircon. 

A mineral of brownish-yellow color is closely associated and sometimes inter- 
grown with the blue amphibole in slide rock northeast of Copper Mountain. It 
occurs in aggregates of minute grains, which appear to be rudely rectangular. 
The index of refraction is below that of the blue amphibole, while the double 
refraction is somewhat higher and extinction is parallel. Further determination 
was impossible. 

Two unknown minerals occur included in some of the analcite. One is present 
in minute, irregular particles, arranged as streams across the analcite grains or 
crowded near the margin. It has higher index than the analcite and polarizes 
very faintly. The other mineral occurs as exceedingly small needles extending 
into the analcite from surrounding mineral grains. It has rather high index, high 
double refraction, and parallel extinction. 

Besides the alteration products already mentioned in the description of the 
important constituents, carbonates, fluorite, and pyrite frequently occur as sec¬ 
ondary minerals near veins. 

TEXTURE. 

Since texture is very largely dependent on the development of the component 
minerals of a rock, the texture of these phonolites has already been partly described. 
The rocks are liolocrystalline and porphyritic, though phenocrysts are often rare. 
The groundmass consists of feldspar microlites with interstitial grains of sodalite, 
aegirine, and the two unknown minerals of aegirine-like habit. Flow structure is 

a Cross, W., General geology of the Cripple Creek district, Colorado: Sixteenth Ann. Rept. U. S. Geol. Survey, pt. 2,1895, 
pp. 30-31. 





60 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

nearly always to be seen, but it is obscure or pronounced according to the develop¬ 
ment of the second-generation feldspar. Automorphic development of the feld¬ 
spars of the groundmass produces the typical trachytic texture which is charac¬ 
teristic of these rocks. In several cases the groundmass feldspars are of poor 
crystallographic form, and then usually associated with small nepheline grains, the 
resulting texture approaching microgranular. 

CHEMICAL CHARACTER. 

The chemical nature of the plionolite magma is expressed in the following 
analyses by W. F. Hillebrand, to which is added the analysis by L. G. Eakins, of 
a bowlder found a few miles north of Cripple Creek, and described by Cross. 


Analyses of phonolites from Cripple Creek.o 



I. 

II. 

III. 

IV. 

V. 

VI. 

SiOs. 

58.98 

58.78 

59.00 

58. 64 

58.85 

60.02 

A1;0 3 . 

20.54 

20.03 

20.07 

19.62 

20.06 

20.98 

FejO;. 

1.65 

1.87 

1.58 

2.17 

1.83 

2.21 

FeO. 

.48 

.49 

.05 

.42 

.51 

.51 

MgO. 

.11 

.16 

.10 

.37 

.18 

Trace. 

CaO. 

.67 

.83 

1.05 

1.24 

.95 

1.18 

Na 2 0. 

9.95 

9.36 

8.34 

8.39 

9.01 

8.83 

K 2 0. 

.5.31 

5.50 

5.63 

5.26 

5. 43 

5.72 

H s O-. 

.19 

.31 

.24 

.34 

.27 

1 70 

HoO+. 

.97 

1.57 

2.03 

2.40 

1.74 

f 

Ti0 2 . 

.24 

.29 

.29 

.20 

.25 


Zr02. 

.20 

. 17 

.20 

.09 

.16 


co 2 . 



.26 

.23 

.12 


P»0„. 

.04 

.03 

.05 

.03 

.04 

Trace. 

so 3 . 

.20 

. 12 

.07 

Trace. 

.10 


Cl . 

.288 

.58 

.24 

.14 

.31 


MnO.. 

.26 

. 15 

.12 

.20 

.18 


BaO.-. 

None. 

None. 

Trace. 

Trace. 

Trace. 


SrO.. 

None. 

None. 

None. 

Trace. 

Trace. 



Trace. 

Trace. 

Trace. 

Trace. 

Trace. 



— 

100.07 

100.24 

99.92 

99.74 

99.98 

100.15 


I. Miter Peak, south-southwest of Grouse Hill. 

II. One mile south of Straub Mountain. 

III. dike. Northeast slope of Big Bull Mountain. 

IV. Dike. Southwest slope of Rhyolite Mountain. 

V. Average of the preceding four analyses. 

VI. Between Cripple Creek and Florissant, Colo. Cross, W., Proc. Colorado Sci. Soc., vol. 2, 1887, p. 167. 

A noticeable feature of these analyses is their very close agreement, though 
they represent rocks from separated localities and of markedly different appearance. 

The most striking chemical feature is the richness in alkalies and the low 
amount of bivalent bases. In these respects the Cripple Creek rocks possibly 
surpass the average plionolite. The ratio of potash to soda is rather greater than 
usual. The considerable amount of combined water is accounted for by analcite. 
Of phonolites described from other localities, the most similar are from the Black 
Hills, South Dakota. The rocks from these two areas show many mineralogical 
as well as chemical likenesses. 


a Cross, W., Sixteenth Ann. Rept. U. S. Geol. Survey, pt. 2, 1895, pp. 38, 39. 



















































TERTIARY VOLCANIC ROCKS-LEUCITOPHYRE. 67 


A calculation of the average analysis, No. V, gives a good idea of the relative 
amounts of the various minerals present: 

Mineral composition of phonolite. 


Soda orthoclase. 51.19 

Nepheline. 11.27 

Analcite. 11.41 

Nosean.89 

' Sodalite... 4. 25 

iEgirine. 4.16 

Augite. 2. 64 


Apatite.09 

Titanite.£1 

Magnetite.48 

Other minerals, hygroscopic water, water of 

hydration, etc. 3.01 


100.00 


This computation is complicated by the presence in the rocks of kaolin, a little 
sericite, and perhaps a small amount of zeolites, resulting largely from the feldspar. 
Careful examination of thin sections of the specimens analyzed led to the conclusion 
that not more than 0.75 per cent H,0 on the average has been introduced by the 
hydration of original minerals. 

The ratio of K 2 0 to Na 2 0 in the soda-orthoclase was assumed to be 33.57:17.32, 
or approximately 2:1. 

The nepheline was considered free from potash. 

The following composition was assumed for augite: CaO, MgO, FeO (Al,Fe) 
20 3 .3 Si0 2 , Al:Fe" ' being 4:1. 

It is probable that the titania is not present wholly as titanite, but occurs 
mainly in other minerals. 

The zirconia forms very little zircon and probably is mostly united in other 
minerals. 

SUMMARY. 


From the preceding discussion it is obvious-that the phonolites of the Cripple 
Creek district are a particularly well-defined group of rocks, and that chemically, 
mineralogically, and texturally they are typical of the recognized phonolite family. 

LEUCITOPHYRE (?). 

In examining a thin section of a specimen of breccia from the dump of a shaft 
about a quarter of a mile north of the Mint mine, on Gold Hill, there was observed 
a small fragment of a rock which has not been seen elsewhere in the district. The 
hand specimen shows a fairly coarse breccia with much granite and latite-phonolite 
and two fragments of a fine-grained, purplish-brown rock, which holds an occasional 
small phenocryst of feldspar and in which the hand lens reveals, in addition, abundant 
minute whitish specks evenly distributed through the mass. Under the microscope 
the rock shows considerable alteration. The feldspar phenocrysts have a patchy, 
uneven extinction and are either microperthite or anorthoclase. The most con¬ 
spicuous constituent is the mineral observed by the hand lens. It forms crystals 
of sometimes square and sometimes hexagonal, but usually octagonal, outline, 
which attain a maximum size of 0.5 mm. The original material is decomposed 
into a zeolite of weak refractive power, and low aggregate polarization. The 
mineral can have been only leucite or analcite. In those rocks which contain 
phenocrysts of analcite, the analcite is seldom abundant and generally occurs in 















68 


GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


good-sized individuals of imperfect crystal outline. But the mineral in question 
is abundant in sharp crystals of small size, and hence is probably not analcite. 
On this account, as well as because of the general character of the rock in which 
it occurs, the mineral is considered to be leucite. A number of small rectangles 
of nepheline, now somewhat altered, occur in groups here and there. A few grains 
now replaced by carbonate suggest the original presence of a sodalite mineral. 
The outlines of what were probably pyroxene phenocrysts are preserved in a few 
cases. Several good-sized grains of magnetite are present. The groundmass is 
quantitatively important, but now much decomposed. The only recognizable 
constituent is orthoclase in narrow laths. The interstices between the feldspar 
are turbid and stained deep brown, probably by iron, which may have resulted 
from the oxidation of minute grains of aegirine such as occur in the phonolites. 
The texture is trachytic, with fluidal structure imperfectly shown, and with a trace 
of intersertal texture suggests a relation to basalts. 

This rock could probably never have been present in great amount or it would 
have been detected elsewhere. The existence, however, of even a small amount 
of a potash-rich leucite rock as a product of a magma essentially sodic® is of more 
than passing interest. 

LATITE-PHONOLITE. 

GENERAL DESCRIPTION. 

Necessity for a new division .—There are present in the Cripple Creek dist rict 
numerous intrusive masses which give evidence of close relationship. They are 
composed of rocks, similar or identical in appearance, which study shows to be so 
closely related that they constitute a definite and distinct rock type. Although 
this type shows certain mineralogical and chemical relations to plionolite, trachyte, 
latite, and trachydolerite (or essexite), and although its extreme facies, if considered 
by themselves, might, perhaps, be placed in some of these well-known families, 
nevertheless when account is taken of the close interrelation of all the facies it 
becomes plain that even the extremes are bound more closely to one another than 
to somewhat similar rocks within the near-by divisions. This type, therefore, 
though w y ell defined, does not correspond with any of the rock groups generally 
recognized, but instead occupies an intermediate position. In view of the principal 
relationships which these rocks show and which it is desired to emphasize, they 
have been given the name latite-phonolite. 

Definition .—It is proposed to apply the name latite-phonolite to those por- 
phyritic rocks which have a composition intermediate between that of plionolite 
and that of latite. To make this term definite and specific it will be well to give 
exact definitions of both latite and plionolite. Plionolite is used, in the sense 
already employed, to designate a rock containing high alkalies and alumina with 
moderate silica and 1ow t bivalent bases, characterized by the presence as pheno¬ 
crysts of alkali feldspar, nepheline, and an alkali pyroxene. Latite, 6 a rock 
intermediate between trachyte and andesite, and the porphyritic equivalent of 
monzonite, contains moderate amounts pf silica, iron, magnesia, and lime, plentiful 
alumina, and notable alkalies of which potash is most prominent, and is commonly 


a See p. 113. 


b Ransome, F. L., Am. Jour. Sci., vol. 5, No. 29, 1898, p. 372. 







TERTIARY VOLCANIC ROCKS-LATITE-PHONOLITE. 


69 


characterized by phenocrysts of soda-lime feldspar and ferromagnesian silicates 
in a groundmass rich in potash. 

Latite-phonolite differs from phonolite in having lower alumina and alkalies 
and more iron, magnesia, and lime. It differs from latite in having somewhat 
lower silica, iron, magnesia, and lime, and higher alumina and alkalies, with soda 
predominant over potash. It is intermediate between latite and phonolite, chemi¬ 
cally, in having each essential oxide present in an amount which lies between the 
average present in latite and that in phonolite; mineralogically, in that the amount 
of minerals high in alumina and soda—such as nepheline—of the phonolites is 
smaller in the latite-phonolites, that part of the alkali feldspar of the phonolites 
unites with the lime-rich feldspars of the latites to give a rather alkalic plagioclase, 
and that the dark silicates are intermediate in composition between those of phono¬ 
lite and those of latite. The group thus broadly characterized shows, as is not 
uncommon in high alkali rocks, a notable prominence of lime over magnesia. 

Such a composition, of course, allows the development of orthoclase and albite 
molecules, and the considerable lime, low magnesia, and plentiful alumina necessi¬ 
tate the formation of a comparatively small amount of the anorthite molecule. 
Both orthoclase and sodic plagioclase are thus characteristic minerals of this group. 
For true phonolite nepheline is considered one of the essential components, but in 
this group, at least, it seems desirable to make the distinctions chemical rather than 
mineralogical by giving to each of the minerals analcite, sodalite, and nosean a 
classificatory rank equal with nepheline. The last two minerals have practically 
the same ratios of silica, alumina, and soda as nepheline, and in analcite only the 
silica is a little different; it is probably only because of the presence in the magma 
of water, chlorine, or sulphuric anhydride, respectively, that these minerals form 
instead of nepheline. Pyroxene or amphibole are common constituents. The) T 
are often alkalic, always low in magnesia, and contain a large percentage of the 
total lime ol the rock. Mica, if present, must, on account of the low magnesia, be 
an iron-rich variety, like lepidomelane. Apatite and sphene are often noteworthy 
accessories and help to utilize the lime. 

The characteristic minerals of the latite-phonolites are therefore orthoclase, 
sodic plagioclase, a soda feldspathoid (including analcite), and some mineral of the 
pyroxene, amphibole, or mica groups. The proportions of essential oxides consid¬ 
ered to represent a typical latite-phonolite are here given: 

Typical composition of latite-phonolite. 

SiOo. 55.00 MgO . 1.00 

A1 2 0 3 . 19. 00 CaO . 4. 00 

FeO J. 50 | K 2 0. 4.50 

These rocks show affinities to several surrounding types besides phonolite and 
latite. The relation to trachyte is in many ways very close. In fact, the term 
trachyte-phonolite is almost as correctly applicable to these rocks as latite-phonolite. 
Silica is lower than in trachyte and alumina and ferric iron a little higher, while lime 
is noticeably more abundant. The amount of alkalies is slightly greater, but the 
ratio of soda to potash is inverted. These chemical differences from trachyte 









70 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


reveal themselves principally in the presence of lime-bearing feldspars and of 
nepheline, analcite, sodalite, or nosean, minerals which contain a higher ratio of 
alumina and alkalies to silica than the alkali feldspars. The alkali-syenite porphy¬ 
ries of Rosenbusch show close relationships to this group. The trachyphonolites 
or oligoclase-sanidine phonolites of Boric,ky a are very similar and would be 
included in this type. The monzonite-porphyries differ, of course, in the same way 
as theh equivalents, the latites, having lower alumina and alkalies and notably 
higher magnesia. The trachydolerites (or essexite porphyries), which partake in 
part of the alkaline character of phonolite, though richer in bivalent bases than latite, 
present certain relations to this type. 

The latite-phonolites of the Cripple Creek district include the trachytic phono¬ 
lites, syenite porphyries, and andesites described in the earlier report. The recent 
study, with its greater advantages, has shown the impossibility of making such a 
separation. Individual rock masses frequently exhibit as wide variations as are 
found in the whole group. Although these rocks are decidedly variable in texture, 
and not exactly identical in composition, all the evidence—areal, structural, macro¬ 
scopic, microscopic, and chemical—goes to prove that they are intimately related 
and are variants of a well-defined rock type. The connection of /these latite- 
phonolites with the true phonolites of the district, as shown by the transition mem¬ 
bers and by the chemical composition (see p. 79), is an interesting feature, and since 
latites are absent in the district and it is desired to bring out the close connection 
between all these volcanic rocks, this relation to the phonolites rather than to the 
latites is emphasized in the following description. In the other direction these rocks 
grade texturally and constitutionally into the essexitic syenites, which are described 
on page 84. They are holocrystalline porphyries made up of monoclinic 
and alkali-rich triclinic feldspars, abundant pyroxene, and analcite, sodalite, or 
nosean, while ampliibole and biotite are often present. A biotite facies of trachytic 
composition is described on pages 77-78. 

Occurrence .—These rocks are less abundant than the phonolites in the Cripple 
Creek district and are found principally in the vicinity of the volcanic center. Like 
the phonolites, they are in part older and in part younger than the breccia. They 
rarely occur in the outlying granite, and then only as small dikes. Large intrusive 
masses, of which many are now reduced in size through brecciation, occur in and 
on the slopes of the amphitheater between Battle Mountain, Bull Cliff, and Bull 
Hill and extend over on the southwestern slope of the latter. Bodies of consider¬ 
able size also occur on the southeastern slope of Battle Mountain, on the northeast¬ 
ern sides of Bull Hill and of Bull Cliff, on the gentle slope north of Big Bull Moun¬ 
tain, and south of the summit of Gold Hill. Mine workings show that a number 
of these large masses are flat and that in some cases they have a greater extent 
than their surface exposures would indicate. In one case, that of the crescentic 
mass near the Isabella mine, the latite-phonolite body narrows rather rapidly to a 
dike about a thousand feet below the surface. Smaller masses or irregular dikes 
are found near Anaconda and near the Gold King mine in Poverty Gulch and are 
seen in several other places underground. 


a Archiv der Naturwiss , Landesdurchforschung von Bohmen, vol. 3, pt. 2 1884, pp. 42-49, 60. 




TERTIARY VOLCANIC ROCKS-LATITE-PHONOLITE. 


71 


Appearance. —The latite-phonolites are dark-gray to black rocks, usually of 
rather fine grain. They are porphyritic in texture and contain small prismatic 
phenocrysts of pyroxene and tablets of feldspar up to 2 cm. diameter. Small scales 
of brown biotite are observable in some varieties, and fresh, smoky apatites in short 
hexagonal crystals up to 2 mm. diameter in cross section are frequently seen. 
Occasional small, resin-yellow crystals of titanite are apparent in hand specimens. 
The groundmass is compact and dark in color. Some of the rocks, however, 
appear to be granular, and only with the aid of the microscope are found to contain 
a microlitic groundmass. This phase marks the gradation into the granidar sye¬ 
nites. Small included fragments of syenite appear in the zone of transition to the 
granular rock. In some specimens these inclusions appear to be partially dissolved 
and absorbed by the surrounding rock, which there contains more hornblende— 
a prominent mineral of the inclusion—than elsewhere. 

Upon weathering the feldspars and the groundmass become dull and lighter 
colored, giving a gray color to the rock. More complete change usually produces a 
light yellow color, as in the phonolites, and at such times the pyroxene phenocrysts 
may be entirely removed, giving the characteristic porous or pitted appearance 
seen near the Blue Bird mine. Even in the most decomposed portions apatite 
remains fresh and glassy and often serves to identify the rock. 

MINERALOGICAL CHARACTER. 

General statement .—The essential minerals ofi these latite-phonolites are alkali 
and soda-lime feldspars, analcite or sodalite or nosean, pyroxene, both augite and 
aegirine-augite, and a brown hornblende. Biotite sometimes becomes important 
and produces a type somewhat different from the common one. The close relation 
to the true phonolites is shown among other ways, by the presence of nosean, 
sodalite, and analcite. Titanite, apatite, and black iron ore are noteworthy acces¬ 
sories and a few minerals present in smaller amount will be mentioned and briefly 
described later. Among the decomposition products are kaolin, sericite, chlorite, 
serpentine—and possibly talc—epidote, green mica, rutile, quartz, and carbonates. 

Variations in. the mineralogical character of this group make it more complex 
than the phonolites; but as will be seen later, the chemical composition is notably 
constant, and therefore recpiires a nice equilibrium between the amounts of the 
alkali-rich and the iron, magnesia, and lime-bearing minerals. The presence of 
nosean, sodalite, or analcite is offset by an increase in pyroxenes or hornblende 
and a decrease in feldspar. The groundmass feldspars are almost without excep¬ 
tion alkali-feldspar. When the feldspar phenocrysts are abundant, they are usually 
rather alkalic; when decidedly calcic, they are never numerous. 

A decrease in the amount of bivalent bases and consequent increase in silica 
causes the ferric iron to enter largely into the formation of a brown mica, which 
must therefore correspond to the variety lepidomelane. The rock thus produced 
is rather different from the pyroxene-rich type and while showing close chemical 
affinities is distinguished by the name biotite trachyte. It occurs on the northern 
slope of Battle Mountain and the northwestern slope of Mineral Hill. Varying 
amounts of botite in the more typical latite-phonolites show the close relation of 
the two varieties. 


7 2 


GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


Feldspar .—Orthoclase is common in phenocrysts from 0.05 lip to more than 
1 cm. in size. Columnar crystals parallel to the clino-axis have fairly good basal 
and pinacoidal faces. Tablets parallel to the clinopinacoid are usually of poor 
crystallographic outline, though the base is sometimes well developed. Carlsbad 
and occasionally Baveno twinning is seen. Cleavage appears to be less perfect 
than in the phonolites. The angle of the position of extinction with the basal 
cleavage sometimes indicates soda-orthoclase. The usual product of decomposition 
is kaolin, while sericite forms near mineral veins. 

Several species of triclinic feldspar occur as phenocrysts. Microcline is present 
sparingly in a few rocks. Microperthite, with its characteristic patchy and flaky 
extinction, is frequently seen. A few individuals may be referable to anorthoclase, 
but not with certainty. The most important phenocrysts of these rocks belong 
to the ordinary plagioclase group, and range from albite to labradorite inclusive. 
The variety which is by far the most plentiful appears to correspond to a compo¬ 
sition between albite and oligoclase, while species more calcic than oligoclase are 
uncommon. Calculation from analyses shows that only about 1 per cent of the 
total lime of the rock enters into the plagioclase. The phenocrysts are usually 
tabular parallel to the brachypinacoid and have rather imperfect crystallographic 
boundaries. In some cases, however, they occur as stout prisms bounded by 
well-developed pinacoids, base and macrodome. Albite twinning is almost invariably 
present, but because of the frequency with which clinopinacoidal sections showing 
no twinning are met, the importance of plagioclase is at first underestimated. 
Carlsbad and pericline twinning sometimes also occur, and in one case albite and 
Baveno twinning occur in the same individual. Zonal structure is very common. 
The change is gradual and uniform and follows the usual order of solidification. 
Particularly in those rocks with abundant feldspar phenocrysts and subordinate 
groundmass it is common to find the plagioclase bounded by a zone filled with 
minute gas bubbles and opaque inclusions, and then surrounded by a narrow rim 
of clear orthoclase. This orthoclase mantle appears to develop more on the pina¬ 
coids than on the base, sometimes leaving the latter face wholly uncovered. Occa¬ 
sionally a micropegmatitic or perthitic intergrowth of plagioclase and orthoclase 
is observed. Small brownish isotropic patches of irregular form occur without 
definite distribution through some of the larger individuals and represent inclusions 
of glass. Microlites or small irregular grains of pyroxene are sometimes also 
included in the plagioclase. 

Kaolin is the chief product of 'weathering. Epidote results under certain 
conditions from alteration of the calcic feldspars. A very interesting decomposition 
results in a pseudomorphic change of the feldspar into a colorless isotropic material 
of low refractive index. The transformation begins along cracks and cleavages, 
forming a meshwork around unaltered kernels, and in most specimens the 
plagioclase has been entirely replaced. This decomposition has been noted only 
in those plagioclase individuals which are surrounded by the mantle of orthoclase, 
and in every case the monoclinic feldspar remains clear and unaltered. When a 
thin section containing this decomposition material was warmed with dilute 
hydrochloric acid and then treated with fuchsine, the area within the orthoclase 
rims absorbed the dye. This test strengthens the conclusion drawn from the 


TERTIARY VOLCANIC ROCKS-LATITE-PHONOLITE. 


73 


optical properties—that the mineral is analcite. In some cases grains of calcite 
are embedded in the analcite and probably owe their existence to the presence of 
lime in the original feldspar. 

Another decomposition product of the feldspars, perhaps both orthoclase and 
plagioclase, appears as a foliated or fibrous mass usually oriented parallel to some 
face of the feldspar phenocryst. It is colorless, has a refractive index somewhat 
higher than that of Canada balsam, and gives parallel extinction and interference 
colors in yellows and reds of the first order in sections of usual thickness. These 
properties and the mode of occurrence correspond to alunite. But a test of a rock 
in which it was abundant failed to give a reaction for sulphuric acid, and alunite 
is hence excluded. The mineral corresponds in some ways to hydrargillite, but 
its identity is not established. Sericite results to some extent from the plagioclase 
also in the vicinity of mineral veins. 

Of the groundmass feldspars, orthoclase is by far the most abundant. Albite 
specimens are present in a few. The habit of these youngest feldspars is similar to 
that in the phonolites. The lath forms are most common, but small flakes of 
iregular outline are often observed. 

Pyroxene .—This mineral group is an important constituent of the iatite- 
phonolites. Phenocrysts up to 1 cm. or more in cross section, frequently as 
anhedrons, a but more often of definite crystal form are, because of their habit, 
and the composition of the magma, necessarily augite. They are usually of pale 
green color, slightly pleochroic to light greenish yellow. Prismatic cleavage is 
fairly well developed, c: c is always over 40° and frequently rises to 58° or 60° 
in which case the colors are deeper, the pleochroism more marked, and the mineral 
becomes aegirine-augite. The interference colors are rather high. Arrangement 
in zones of slightly different composition is a rather common feature, and twinning 
parallel to the orthopinacoid is not unusual. Large individuals sometimes inclose 
grains of feldspar, and in certain instances an interpenetration with hornblende 
is well shown. 

Pyroxene is generally abundant in the groundmass. In some specimens it 
occurs in little bundles and sheaves of green needles and grains, much as in the 
phonolites. In a few others it forms narrow laths with intersertal distribution. 
The most common occurrence is as microlites and small rounded grains rather 
evenly scattered among the groundmass feldspars. 

The most common alteration is to carbonates, black iron ore, and chlorite; 
occasionally quartz also may be seen. Serpentine is sometimes a product, epidote 
forms at times, and not infrequently a mass of light-green secondary mica (described 
on p. 77) replaces and retains the form of the p}"roxene individual. 

Hornblende and biotite .—Hornblende is not unfailingly present, but usually occurs 
in individuals of fairly good form and moderate size. Occasionally it becomes quite 
prominent. It is strongly pleochroic in browns and yellows and shows absorption 
as follows: c > b > "*, c and b often being not very different. Cleavage is distinct as 
usual. Twinning is not uncommon. The maximum extinction angle in clino- 
diagonal sections is 26°. Intergrowth with pyroxene is common and sometimes the 
latter is completely surrounded by a fairly even rim of hornblende. Corrosion has 


a Pirsson, L. V., Bull. Geol. Soc. America, vol. 7, 1896, p. 492. 







74 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

sometimes taken place and resorption, or magmatic alteration into pyroxene and 
magnetite, is a usual phenomenon. The borders of pyroxene grains sometimes have 
the same orientation as the hornblende core, but are as frequently without definite 
arrangement. They seem to have about the same composition as the original 
augite. Magnetite is less plentiful in the rocks containing considerable unchanged 
hornblende. Chlorite, serpentine, and the secondary green mica often result from 
decomposition. 

Biotite is frequently absent, but in many specimens occurs sparingly. In a few 
varieties it becomes the predominant ferro-magnesian constituent owing to a slight 
variation in the chemical character of the rock, as already noted (p. 71). It is 
probably related to the variety lepidoinelane. It is reddish brown, with strong 
absorption and sensibly parallel extinction. Corrosion is common and frequently 
the foils are bent or broken. Resorption with the production of abundant magne¬ 
tite, a little pyroxene, and probably some feldspar, occurs in most rocks which contain 
it. Chlorite and the green mica are common alteration products. 

Nosean, sodalite, and analcite .—As has been stated, these minerals are of inter¬ 
est as indicating a close relation of these rocks to the phonolites of the district. It 
may also well be repeated that in those rocks in which these minerals are at all 
plentiful the richness in alkalies which they indicate is offset by a greater abundance 
of the lime and ferromagnesian minerals than in the phonolites. In a very few 
specimens none or only a slight amount of these minerals has been detected. 

Nosean is present in many rocks and occurs as in the phonolites in phenocrysts 
of good size, usually with the grill-like inclusions. It is often decomposed into a 
more or less faintly polarizing aggregate, probably of zeolites. Other decomposition 
products are analcite and serieite. The occasional presence of grains of calcite 
among the decomposition products in rocks which do not elsewhere contain much 
calcite may indicate that some hauyne is present. 

Sodalite is found in all the nosean-bearing rocks and in a few others. It is 
almost always in the form of minute grains or crystals between the other ground- 
mass crystals, or included in the larger feldspars, but occasionally attains sufficient 
size to be regarded as a phenocryst, and then shows a clear border and a brown 
center crowded with inclusions. 

Analcite is of still more general distribution and occurs usually in irregular 
interstitial grains of small size. In a very few cases it occurs in individuals which 
may be idiomorphic, but with this exception its mode of occurrence and properties 
are exactly as in the phonolites. Small, sharp crystals of augite and of titanite 
which occur embedded in it sometimes entirely separated from other constituents 
necessitate the same conclusion as to its origin as was reached in the treatment of the 
phonolites—that is, it is a primary or original constituent of the rock. The analcite 
derived from the decomposition of feldspar is of course wholly distinct in origin and 
mode of occurrence. 

Apatite .—This mineral is always present to some extent, usually associated with 
iron ore, and often occurs in numerous crystals of notable size. It forms stout hex¬ 
agonal prisms up to 2 mm. in cross section, and is usually terminated by the unit 
pyramid and sometimes also by the basal pinacoid. Shapeless, irregular grains are 
not common, but well-formed crystals have sometimes been corroded. In many 


TEliTTARY VOLCANIC ROCKS-LATITE-PHONOLITE. 


75 


rocks the apatite crystals are crowded with minute inclusions, which probably give 
the smoky color to the mineral in the hand specimens. A high power reveals consid¬ 
erable as to the nature of these inclusions. Some are approximately equidimen- 
sional and rarely reach the maximum diameter of 0.001 mm. From this shape they 
pass by all gradations to the most common form, that of exceedingly slender rods of a 
maximum observed length of less than 0.01 mm., and a cross section which is often no 
more than 0.00002 mm. in diameter and perhaps less. Their distribution throughout 
the crystals is not uniform. Near the prism faces they are always crowded and near 
the terminal planes they diminish in number to almost complete absence. Within 
the body of the crystal they mav be very evenly disposed or on the other hand be so 
crowded about certain lines or along planes that portions of the crystal sometimes 
become opaque. Red or black irregular compact grains of small size but of much 
greater dimensions than those of the inclusions can often be seen, near the edges, to 
be thus built up of innumerable inclusion individuals so closely packed that they have 
coalesced. The larger or stouter forms are distributed mainly along lines or planes, 
which may he slightly curving and which from all appearances have no relation to 
crystallograpliic directions. 

In spite of this lack of uniformity of distribution as regards number and size, 
they have a definite crystallographic arrangement or orientation. The larger inclu¬ 
sions can be seen to possess in general verj* perfect negative crystal form, though 
some are irregular. The slender forms have their long direction parallel to the 
vertical axis and are arranged in rows parallel to the three other axes. 

Great numbers of the inclusions, particularly the larger, stouter ones, have a 
much lower refractive index than the apatite, and the width of their black borders 
suggests that they are fluid inclusions. This idea is confirmed by the presence, in 
many, of a minute round particle with a still broader black rim which can in some 
cavities be seen to be in constant motion and to be influenced by gravity and which 
is beyond question a gas bubble. Some cavities contain, in addition to the liquid and 
the gas, a tiny angular speck which is probably a salt crystal separated out from the 
liquid. 

These inclusions, when obviously fluid, range from nearly or quite colorless 
• through light yellows and reds to brownish yellow, brownish red, or deep red. Many 
of the long and very narrow ones seem to be composed of a solid material, which 
is sometimes red and sometimes black and opaque, with all gradations between. 
Examination of aggregates of these solid inclusions shows that they are composed of 
hematite. 

The foregoing facts appear to justify the following conclusion: At the time 
of the formation of the apatite—that is, near the beginning of the crystallization of 
the magma—water was present in addition to the chlorine or fluorine, or both, of the 
apatite, and it held ferric iron and possibly other bases, in solution. Later a change 
of conditions caused a precipitation of part or all of the iron as hematite, and the 
small solid grains within the liquid may be crystals of a different material. The 
yellow colors may be due to more or less concentrated ferric solutions, maintained 
possibly by pressure or by a small amount of some reagent, such as chlorine. 
•Depending on the amount of hematite which has been deposited on the walls of the 
cavity, the liquid appears more or less red or the inclusion seems to be wholly solid. 


76 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


Many of the apatites thus filled with inclusions exhibit a noticeable pleochroism. 
E is violet and O is smoky brown, and the absorption is E>0. 

Inclusions somewhat analogous in character and arrangement have been 
described in rock-forming apatites from Persia 0 and from Montana, 6 but in neither 
case were fluid-filled cavities mentioned. As observed in both these descriptions 
and also by Washington, c the abundance of inclusions in the apatite in these rocks 
appears to bear a definite relation to the degree of resorption of the hornblende, and 
in this case of biotite also. If the above assumption as to the origin of the inclusions 
in the Cripple Creek rocks is correct, there may be some connection between the 
excess of iron indicated in the inclusions and the later separation of magnetite in the 
resorption process. 

In a specimen of the biotite trachyte from the Portland mine well-formed 
crystals of apatite, reaching a maximum diameter of about 1 mm., are rather com¬ 
mon and on casual examination under the microscope appear to be of normal 
structure. In parallel light, however, indistinct traces of a fibrous structure are 
seen, and when the nicols are crossed the mineral polarizes in a peculiar manner, 
giving aggregate, feathery extinction due to minute fibers confusedly radiating 
from numerous centers or nuclei. The appearance is similar to that which often 
results from the filling of a cavity by quartz deposited from solution. The single and 
double refraction and other optical properties show- that apatite is the only mineral 
present and no explanation of the phenomenon has been found. 

Aside from these pecularities, the occurrence of apatite in these rocks is of 
considerable interest. The number and size of the crystals is rather unusual. A 
noticeable fact is that in the sodalite-bearing rock specimens of this group the 
amount of apatite is considerably less than usual. This may be due to some adjust¬ 
ment or equilibrium between soda, chlorine, and phosphoric anhydride. It is 
possible that there is a concentration of chlorine in the soda-rich (sodalite-bearing) 
varieties and of phosphoric anhydride in those holding less soda. 

The presence of \v r ater (the liquid can hardly be anything else) in the inclusions 
is also of interest when taken in connection with the occurrence of primary analcite. 

Titanite .—Although not unfailingly present, this mineral is a common accessory 
of the latite-phonolites, and sometimes is noticeably abundant. It occurs at times 
as irregular grains, but is more frequently idiomorphic in the diamond-shaped 
forms or the narrow laths, as in the plionolites. Some of the crystals reach a size 
of over 1 mm. The mineral has a brown color and the strong absorption some¬ 
times amounts almost to pleochroism. Twinning is occasionally seen. 

The manner of decomposition of the titanite of these rocks is rather interesting. 
At the outer edge of the crystal is formed a narrow rim of material, only slightly 
transparent, of very high refractive index and double refraction, which corresponds 
to rutile. Narrow arms of this mineral sometimes also extends across the inner 
portion of the crystal. Within this shell of rutile cal cite is plentiful and frequently 
fills the entire cavity, but in many cases there is also present a small amount of a 
mineral of rather low double refraction and an index near that of Canada balsam, 

n Blaas, J., Tschermaks Min. u. petrogr. Mittheilungen, vol. 3, 1880, pp. 477-479. 

t Merrill, G. P., Proc. U. S. Nat. Mus., vol. 17, 1894, pp. 642-643. . 

c Washington, H. S., Magmatic alteration of hornblende and biotite: Jour. Geol., vol. 4, 1896, p. 279. 





TERTIARY VOLCANIC ROCKS-LATITE-PHONOLITE. 


77 


which exhibits aggregate fibrous polarization and can with certainty be called 
chalcedony, lliese three minerals thus form a somewhat complex decomposition 
pseudomorph after titanite. (See PI. XVII, E.) The alteration appears to take 
place with equal readiness away from and near mineral veins. 

Other minerals .—Magnetite occurs rather abundantly, particularly in those 
varieties holding numerous small grains of pyroxene. There is in this fact a pos¬ 
sible significance that the two minerals have resulted from the magmatic resorption 
of hornblende, but it seemed impossible to reach any conclusions as to this matter. 
The mineral occurs especially near crystals of apatite and is usually of later forma¬ 
tion. Oxidation changes it more or less completely to hematite and often it 
furnishes on decomposition an opaque, nearly white, material whose identity could 
not always be established, but which is in some cases certainly a carbonate. Grains 
of partially decomposed black iron ore are sometimes surrounded by minute 
particles of titanite, indicating that part of the iron ore is titaniferous. 

Small brownish crystals of zircon occur in a few varieties. 

In one or two rock masses, particularly in the biotite trachyte on the western 
slope of Mineral Hill, small interstitial grains of primary quartz are evenly dis¬ 
tributed through the groundmass. 

The green secondary mica mentioned as a product of the decomposition of 
pyroxene, hornblende, and biotite does not seem to correspond to any of the varieties 
described in the text-books. It varies from deep grass-green through light and 
greenish yellows to strong yellow or yellowish brown, but is always distinctly 
separable by its color from ordinary biotite. It occurs uniformly as aggregates of 
small fragments, shreds, or fibers which sometimes have an imperfect radial 
arrangement. It is analogous to sericite in texture, but somewhat coarser grained. 
Pleochroism is noticeable in the deeper-colored masses. The polarization colors 
are sometimes rather lower than for either biotite or muscovite, but frequently 
are very brilliant and always have that peculiar character distinctive of the micas. 
Either it has a variable composition or it is built up by the addition or subtraction 
of substance in the minerals from which it forms, for it completely and pseudo- 
morphically replaces pyroxene, hornblende, and biotite, and it is almost certain 
that those minerals do not have identical composition. This change is not limited 
to the vicinity of mineral veins where metasomatism is likely to take place, and it 
is consequently probable that the mineral is variable in composition. 

Near mineral-bearing veins fluorite, carbonates, pyrite, and sometimes a little 
quartz and chalcedony may be introduced into the rock, either as isolated grains or 
as veinlets. In many cases, pyrite partially or completely replaces magnetite, and 
on that account a rock with considerable unaltered magnetite may usually be 
safely assumed to be at some distance from a vein. 

TRACIIYTIC FACIES. 

As has been previously stated (p. 71), a rock which occurs on the northern 
slope of Battle Mountain and northwest of the summit of Mineral Hill differs in 
appearance from the ordinary latite-phonolite by containing numerous small flakes 
of dark-brown biotite. It is the same rock that was called augite-mica andestite by 
13001—No. 54—06-7 



78 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


Mr. Cross. Microscopical and chemical study indicate that, though the rock is 
closely related to the latite-phonolites, it does not conform to the type as do the 
other varities, and the differences are sufficient to put it with the trachytes: it is 
called a biotite trachyte. The Battle Mountain mass appears to be an intrusion 
distinct from the latite-phonolites, but many of the latter contain biotite in amounts 
reaching considerable importance. 

This biotite trachyte contains numerous phenocrysts of feldspar, orthoclase, 
albite, microperthite, and oligoclase or oligoclase-albite being present in decreasing 
amount. Biotite is abundant in scales 1 or 2 mm. across, which are sometimes bent 
and frequently show the common magmatic alteration into augite and magnetite. 
As has been shown on page 74, from the chemical character of the rock this mica 
must be an iron-rich species, probably related to lepidomelane. Phenocrysts of 
augite are occasionally present. Apatite and sphene are rather common in crystals 
of more than ordinary size and grains of magnetite are numerous. Small inter¬ 
stitial grains of quartz occur sparingly in the Mineral Hill rock. Very little analcite, 
sodalite, or nosean has been detected in most specimens. The groundmass is 
imperfectly trachytoidal and consists almost wholly of orthoclase. The chemical 
character of this rock, showing its trachytic nature and its relation to the latite- 
phonolites, is expressed in an analysis given with those of the latite-phonolites on 
the next page. 

TEXTURE. 

These rocks all contain a more or less important groundmass made up of feld¬ 
spar and pyroxene microlites and grains and of particles of iron ore, with sometimes 
plentiful small crystalline grains of sodalite. As in the phonolites, the development 
of the feldspars controls the character of the texture. The most common form is as 
small laths with parallel arrangement showing beautifully the flow movements of 
the magma and giving a trachytic texture similar to that of the phonolites. Like- 
wi e a less perfect crystallographic development of the groundmass feldspars leads 
to a microgranular texture, though fluidal structure can usually be distinguished. 
Abundant development of feldspar in the form of phenocrysts leaves the groundmass 
very subordinate, and in that case it is usually microgranular with little or no 
indication of a flow structure. The very small amount of glass included in some 
of the feldspar phenocrysts is hardly sufficient to warrant classing these rocks as 
other than holocrystalline porphyritic. The principal textural differences between 
the latite-phonolites and the phonolites proper are the greater tendency of the former 
toward phanerocrystalline development, the somewhat coarser grain of their 
groundmass, and their more frequent and decided deviation from the characteristic 
trachytic texture. 


TERTIARY VOLCANIC ROCKS-LATITE-PHONOLITE. 


79 


CHEMICAL CHARACTER. 

The accompanying analyses show the chemical character of the latite-phonolites, 
their range in composition, and their relation to the phonolites: 


Analyses of latite-phonolites from Cripple Creek. 



I. 

II. 

III. 

IV. 

V. 

VI. 

VII. 


5G. 01 

58.05 

54.88 

54. 43 

62.79 

59.38 

58.85 

AljOs. 

17.92 

17.66 

18.53 

19.01 

19.10 

19. 47 

20.06 

FejOa., 

4.20 

3.51 

2.93 

2.85 

2.29 

1.60 

' 1.83 

FeO. 

2.52 

1.65 

1.92 

1.93 

.36 

1.19 

.51 

MgO. 

2.04 

1.55 

1.26 

.99 

.40 

.36 

.18 

CaO. 

4.80 

4.58 

4.15 

4.33 

.87 

1.96 

.95 

Na 2 0. 

4.92 

5.80 

6.65 

6.92 

6.23 

7.80 

9.01 

k 2 o. 

4.21 

4.06 

4.90 

5.07 

5.58 

5.83 

5.43 

H 2 0 -. 

.31 

.35 

.38 

.31 

.25 

.11 

.27 

h 2 o +. 

1.10 

.87 

1.75 

1.68 

.84 

.69 

1. 74 

Ti0 2 . 

1.20 

.91 

.93 

.96 

.71 

.58 

.25 

Zr0 2 . 

.02 

.02 

.03 

.04 

.02 

.10 

.16 

C0 2 . 

None. 

None. 

. 13 

. 14 



. 12 

p 2 o 5 . 

.55 

.40 

.27 

.25 

.12 

.08 

.04 

so 3 . 

None. 

.04 

.36 

.42 

None. 

.37 

.10 

Cl. 

Trace. 

Trace. 

.14 

.22 

Trace. 

.22 

.31 


'.04 

None. 

. 10 

.07 

.10 



Cr 2 0;. 

None. 

None. 





NiO. 

None. 

n. d. 






MnO. 

.13 

.13 

.25 

.08 

.07 

.15 

.18 

BaO. 

.16 

.19 

.18 

.21 

.14 

.13 

Trace. 

SrO. 

.06 

.08 

.11 

.21 

.03 

.03 

Trace. 

Li 2 0. 



Trace. 

Trace. 

Trace. 

Trace. 

Trace. 










100.19 

99.75 

99.82 

100.07 

99.90 

100.05 

99.98 


I. Latite-phonolite, Portland mine, level 6. 

II. Latite-phonolite, Anaconda mine, adit level. 

III. Latite-phonolite, Portland mine, adit level. 

IV. Latite-phonolite, 3,300 feet S. 10° E. from Bull Cliff. 

V. Biotite trachyte, Portland mine, 500-600 foot level. 

VI. Latite-phonolite, south slope. Bull Cliff. Cf. Cross, W., Sixteenth Ann. Rept. U. S. Geol. Survey, pt.2,1895,p. 43. 

VII. Average analysis of Cripple Creek phonolites (V of table on p. 66). 

Analyses I and II by George Steiger; III-VI by W. F. Hillebrand. 

I. A gray rock, showing numerous small phenocrysts of pyroxene and a few 
of feldspar in a fine-grained groundmass. The microscope shows the larger feld¬ 
spar crystals to be between oligoclase and andesine, often bordered by orthoclase. 
The pyroxene is pale green, slightly pleocliroic, and has a large extinction angle. 
Aggregates of pyroxene and magnetite grains in some cases possess the outline of 
hornblende, while in others the resorption is seen to be destroying biotite. Some 
large grains of magnetite and large apatite crystals are present. All these are 
contained in a predominant trachytic groundmass which is a little decomposed, but 
seems to be made up almost exclusively of orthoclase laths, with a very small amount 
of sodalite in tiny grains. Analcite can not be identified. This facies is closely 
related to the latites and is the extreme in that direction of the latite-phonolite 
type. It occurs in the Portland mine, but has been found in few other places. The 
specimen is slightly decomposed. • 




























































80 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


II. A rather light-gray rock, containing occasional small feldspar phenocrysts 
and many small lath-shaped prisms of pyroxene, which indicate direction of flow, 
in a very finely granular groundmass. In thin section the larger feldspars are seen 
to be orthoclase, microcline, and microperthite, with a larger amount of a zoned 
plagioclase, which corresponds to oligoclase-albite. The phenocrysts of pyroxene 
usually have good crystal outline and are not uncommonly twinned; micropegmatitic 
intergrowth with hornblende and with feldspar is sometimes seen. Hornblende is not 
plentiful and is usually surrounded by a zone of pyroxene and magnetite, indicating 
resorption. A few foils of biotite are present. Irregular grains of magnetite are 
common. Apatite and titanite occur sparingly in sharp crystals. Small grains 
of sodalite and patches of analcite are inclosed in fresh feldspar phenocrysts. The 
groundmass is very fine grained, but shows a distinct trachytic texture. The 
minute feldspar laths are too turbid for identification, but are probably orthoclase. 
Microlites of pyroxene and tiny grains of magnetite are plentiful. This specimen 
is from the Anaconda tunnel. The rock appearing above on the surface was desig¬ 
nated on the earlier map as syenite-porphyry. 

III. A finely granular rock of rather dark-gray color, containing plentiful 
phenocrysts and irregular grains of pyroxene and noticeable yellow crystals of 
sphene. Under the microscope it is found to be composed mainly of large and 
small crystals of feldspar, often of diamond-shaped outline. These crystals are as 
calcic as oligoclase in the interior, and are bordered by a zone of orthoclase. Pyrox¬ 
ene is fairly plentiful, both in sharp crystals and irregular grains. It is light green, 
noticeably pleochroic, and has an extinction angle corresponding to aegirine-augite. 
Hornblende is not uncommon, but is usually surrounded by resorption rims. Anal¬ 
cite occurs in partially decomposed masses, sometimes giving a suggestion of crys¬ 
talline outline. Nosean is fresher, in crystals of square outline. Apatite, mag¬ 
netite and noticeable titanite are the accessories. The groundmass is decidedly 
subordinate. Microlites of feldspars, some of which seem to be albite, and tiny 
grains of sodalite, pyroxene, and magnetite are the chief constituents. This 
specimen represents much of the mass occurring on the south slope of Battle 
Mountain, in the vicinity of the Portland mine. 

IV. A rather dark-gray rock, containing small phenocrystic grains of feldspar, 
pyroxene, and a little hornblende in a predominant fine-grained groundmass. 
Microscopic examination reveals abundant feldspar, usually in individuals of imper¬ 
fect crystallographic form. Many of the larger phenocrysts are orthoclase, often 
intergrown with a finely striated oligoclase-albite. Some sodic plagioclase has both 
albite and pericline twinning resembling microcline; outer zones of orthoclase are 
commonly present. The pyroxene corresponds to aegirine-augite in composition, 
but possesses the augite outline. Hornblende, which is not plentiful, occurs never¬ 
theless in individuals of good size. It has suffered some resorption. Nosean is 
rather prominent in turbid crystals of good size. Analcite is also common, but is 
somewhat decomposed into other zeolites, probably stilbite and natrolite. Sodalite 
is not readily distingu'shed, occurring as minute crystals in the somewhat turbid 
groundmass. Apatite, magnetite, and titanite are prominent accessory constit¬ 
uents. The groundmass, though not as abundant as the hand specimen indicates, 
is prominent notwithstanding. It is composed chiefly of laths of orthoclase, with 
small grains of pyroxene, sodalite, and magnetite, and has the trachytic texture. 


TERTIARY VOLCANIC ROCKS-LATITE-PHONOLITE. 


81 


This specimen from Bull Cliff is a good representative of the latite-phonolite 
type, both in composition and appearance. Masses of the same variety occur 
south of Altman, in the vicinity of the Last Dollar mine, on the north slope of Big 
Bull Mountain, and probably on the north and west slopes of Bull Hill, though 
decomposition at those places is too great to justify a conclusion. 

V. This specimen is described on page 71. It represents masses on Battle 
Mountain and on Mineral Hill. 

VI. This is a dark-gray rock, rather granular in appearance, with large and 
small phenocrysts of feldspar, and only little pyroxene visible. The microscope 
shows that the larger phenocrysts are orthoclase, probably rich in soda; the smaller 
ones are a soda-rich plagioclase, some being albite, some oligoclase-albite. The 
pyroxene crystals, which are well developed crystallographically, are segirine-augite. 
Original hornblende is almost wholly resorbed. Nosean is comparatively abundant 
in clouded crystals. Sodalite, which is of lighter color, is less common as pheno¬ 
crysts, but is plentiful in small grains and crystals in the groundmass. Analcite 
can not be identified with certainty, but is probably preserft as inclusions in some of 
the feldspar phenocrysts. Nepheline is absent. Magnetite, apatite, and titanite 
are present in irregular grains and in sharp cr 3 r stals. The groundmass is beautifully 
trachytoid, consisting principally of tiny laths of orthoclase, with microlites of 
pyroxene, sodalite, and magnetite. This rock is closely related in chemical composi¬ 
tion to the phonolites. The specimen is from the same mass as No. IV and thus 
affords a good illustration of variation in a single mass. 

The characteristic chemical features of these rocks are high alkalies, with 
plentiful alumina and moderate amounts of the bivalvent bases. The amounts of 
phosphorus pentoxide (from apatite) and of titania (mainly from sphene) are note¬ 
worthy. The main distinctions from the phonolites are greater variability in com¬ 
position, lower alkalies, and higher lime, magnesia, and iron. 

Of the specimens analyzed, Nos. Ill and IV best represent the type and their 
agreement in composition is very close. It is interesting to note, in passing, that 
No. IV has a predominant groundmass, while in No. Ill the groundmass is subor¬ 
dinate^—a good example of different textural development with constant composi¬ 
tion. A calculation from the analyses of these two specimens, in connection with 
a study of the thin sections, gives an idea of the proportionate amounts of their 
mineral constituents. The appended list is approximate only, because of the num¬ 
ber of independent factors entering into the calculation: 

Mineral molecules in latite-phonolite. 


Orthoclase. 29. 75 

Albite. 26. 10 

Anorthite. 3. 08 

Sodalite. 2.74 

Nosean.-. 3. 53 

Analcite. 4. 60 

.iEgirine.-. 1.02 

Augite. 10.23 


Hornblende. 5.63 

Apatite... 2. 37 

Titanite. 2. 36 

Magnetite. 1.96 

Other minerals, hygroscopic water, water of 

hydration, etc... 6. 63 


100.00 

















PLATE VIII. 

Photomicrographs of Rocks. 

A, Latite-phonolite (624 C. C.) from southern slope of Bull Cliff. Composed of soda-orthoclase, plagioclase, 

nosean, sodalite, segirine-augite, and augite. Augite shows twinning. Nosean is crowded with dark 
inclusions except at the border. Magnified 28 diameters. 

B, Same with crossed nicols. Shows flow structure. Magnified 28 diameters. 

C , Syenite (333 C. C.) from dump of Last Dollar mine. Composed of soda-orthoclase, segirine-augite, augite, 

and hornblende. Magnified 28 diameters. 

D, Trachydolerite (381 C. C.) from summit of Bull Cliff. Composed of orthoclase, analcite, augite, biotite, 

and magnetite. Magnified 28 diameters. 


U. S. GEOLOGICAL SURVEY 


PROFESSIONAL PAPER NO. 54 PL. VIII 



C B 


PHOTOMICROGRAPHS OF LATITE-PHONOLITE, SYENITE, AND TRACHYDOLERITE. 















TERTIARY VOLCANIC ROCKS—LATITE-PHONOLITE. 


83 


This calculation is based oil the assumption, suggested by an examination of 
the thin sections, that the pyroxene is about double the amount of the hornblende. 
It also assumes that the ration of segirine to augite is 1:10,° and that half the water 
given off above 100° represents primary water, and rests on the following arbitrary 
but more or less probable compositions assigned to the augite and hornblende: 

Augite = Ca(), MgO, Fe0(Al,Fe) 2 0 3 , 3Si0 2 , the ratio of A1 : Fe"' being 4 : 1. 

This is the same formula as that used for the phonolites (p. 67). 

Hornblende = CaO, 2MgO, 2FeO, 3(Al,Fe) 2 0 3 ,6SiO ? , the ratio of A1 : Fe'" being 13:1. 

Since the aegirine is united with the augite to form a single pyroxene mineral, 
and since the albite and anorthite form an intermediate plagioclase, oligoclase- 
albite, the following table expresses as accurately as possible the kind and relative 
amounts of the mineral components of these rocks: 


Mineral coniposition of latite-phonolite. 


Orthoclase b . 29.75 

Oligoclase-albite (approximately Ab s A n i) _- 29. 18 

Sodalite. 2. 74 

Nosean. 3. 53 

Analcite. 4. 60 

Soda-augite.-. 11.25 

Hornblende. 5. 63 


Apatite. 2. 37 

Titanite. 2. 36 

Magnetite. 1. 96 

Other minerals, hygroscopic water, water of 

hydration, etc. 6. 63 


100.00 


TRANSITIONS TO PHONOLITE. 

In the course of the mapping and study of the Cripple Creek rocks, three varie¬ 
ties have been found which show, each in a somewhat different way, a mineralog- 
ical gradation of latite-phonolite into phonolite, or vice versa. This is what one 
would expect from the chemical relations just given. These three varieties will be 
briefly described, most emphasis being placed on the points which show the relation 
of the one group to the other. 

On the upper southern slope of Bull Cliff occurs a fine-grained rock, holding an 
occasional small feldspar phenocryst and showing, by slight decomposition, the 
fluidal arrangement of its groundmass feldspars. It strongly resembles the phono¬ 
lites in appearance and seems in the field to grade directly into that type. The 
microscope confirms this similarity, and shows a few narrow feldspar phenocrysts, 
many grains of jegirine, and small phenocrysts of segirine-augite, a few decomposing 
nosean crystals, numerous minute grains of sodalite, but only an occasional small 
crystal of nepheline near or in the irregular analcite grains. 

In a railroad cut on the east side of Battle Mountain, near the Rigi mine, is 
exposed a rock, a little of which is fairly fresh, which appears to be a contact facies, 
or rather marginal facies, of the large latite-phonolite area occurring east and south¬ 
east of the Portland mine. It is brownish gray, considerably mottled, nearly or 

a It happens that the molecular weights of oegirine and of the augite chosen are identical. 

* It is probable that a small amount of the soda calculated as plagioclase enters into the composition of orthoclase. leav¬ 
ing the plagioclase a little more calcic than AbjAni. 



















84 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

* quite aphanitic, and in appearance resembles rather the phonolites than the latite- 
phonolites. Microscopically it is characterized by a number of small lath-shaped 
feldspar phenocrysts, considerable segirine, aegirine-augite, and blue amphibole, 
and irregular, interstitial masses of analcite, in a well-defined trachytic ground- 
mass. Between the feldspar microlites occur numerous grains of sodalite. Nephe- 
line, however, could not be identified with certainty, though a number of minute 
partially decomposed grains of higher index of refraction than the feldspar roughly 
correspond in outline to nepheline. The aegirine occurs in its usual tabular habit, 
but the aegirine-augite takes the more prismatic form of the ordinary pyroxenes. 
The habit of the pyroxene and the scarceness or entire absence of nepheline places 
this rock between the two main groups, but somewhat nearer to phonolite than to 
latite-phonolite. 

The third variety occurs south of the main street of Altman, just west of the 
Deadwood mine. It forms part of a large area of latite-phonolite and appears 
to be identical with the finer grained varieties of that group. Besides numerous feld¬ 
spar tablets and laths of good size, it contains large and small nosean crystals, clear 
little grains and ragged patches of pure aegirine, phenocrysts of aegirine-augite and 
augite, large grains of titanite, abundant sodalite microlites, and small shreds of 
the unknown mineral of high index and double refraction found in the phonolites, 
all contained in a comparatively coarse-grained trachytic groundmass. One or two 
rectangular sections of a partially decomposed mineral may be nepheline. 

It is thus seen that though the phonolites are a particularly well-characterized 
group and the latite-phonolites are fairly well defined, a few intervening members 
reveal the close relation of the two and unite them all into one rock series. 

SYENITE. 

GENERAL DESCRIPTION. 

Granular rocks closely resembling and connected by textural gradations with 
the latite-phonolites occur in various parts of the volcanic area. The larger masses 
were mapped by Cross and called by him nepheline syenite. In the recent study, 
however, no nepheline has been found. Cross’s statement of the presence of this 
mineral is not very conclusive and seems to have been based mainly on the presence 
of decomposition products supposed to have been derived from nepheline. 01 These 
syenites are alkali-rich rocks and are most closely related to the alkali syenites of 
Iiosenbusch; but because of too high lime and magnesia and rather low silica, they 
are in the following description classed broadly as syenites and confined to certain 
characteristics. They show certain affinities to the essexites, but differ in being 
decidedly lower in iron, magnesia, and lime; richer in alkalies, particularly potash; 
and somewhat higher in silica and alumina. They have lower bivalvent bases and 
higher alkalies than the monzonites. While a little more basic than their porphy- 
ritic equivalents, the latite-phonolites, exemplifying a common difference between 
the granular and the porphyritic rocks, 6 they nevertheless show certain close rela¬ 
tionships not only to that rock type, but to the phonolites as well. On the other 

a General geology of the Cripple Creek district, Colorado: Sixteenth Ann. Rept. U. S. Geol. Survey, pt. 2, 1895, p. 44. 
i>Cf. Rosenbusch. H., Elemente der Gesteinslehre, Stuttgart, 1901, p. 249. 


I 





TERTIARY VOLCANIC ROCKS-SYENITE. 


85 


hand, their divergencies from these two types are of such a character as to relate 
these syenites to the more basic rocks whose descriptions follow. They thus form 
another step in the increasingly basic series which begins with phonolite and ends 
with basic dike rocks. 

In appearance they are medium to dark gray rocks, with prominent prismatic 
crystals of pyroxene in a feldspathic matrix. They are distinguished in the field 
with difficulty and not always with certainty from the coarser-grained types of 
latite-phonolite. Weathering or other alteration produces changes that are iden¬ 
tical with those of the related porphyritic rocks, the resulting mass being usually of 
lighter color and more or less porous. 

These granular rocks are not very liberally distributed. The Vindicator mine 
is near the center of the largest area, which is about 2,000 feet in diameter. Another 
mass of some size occurs near the Last Dollar mine, and smaller bodies are found near 
the Rose Nicol mine on the northeast side of Battle Mountain, west of the Logan 
mine on Bull Hill, and in the vicinity of the Pointer mine on Gold Hill. Granular 
rocks referable to this class are also encountered in masses which do not reach the 
surface in the Mollie Kathleen, Granite, and Portland mines and in the Ophelia 
tunnel. 

The gradation to latite-phonolite is well shown on the surface both east and 
west of the Vindicator mine and near the Last Dollar mine and is strikingly seen 
in the underground workings of the Portland, Last Dollar, and Vindicator mines. 
Sometimes, however, there is a sharp contact of intrusion between the two, as shown 
in the Vindicator mine. The nature of the two groups of rocks and their manner 
of occurrence make it probable that only a slight difference in conditions, such as 
change of temperature or pressure, or minor variations in composition, were needed 
to cause the one or the other to crystallize from the magma. There is little or no 
evidence available to show that the granular rock is the deep-seated equivalent of 
the porphyritic.- The transition from one to the other is apparently regardless of 
distance from the surface or from contacts. It is probable that these granular 
rocks have formed much nearer the surface than is believed usually to be the case, 
for erosion since the volcanic period does not appear to have been very great. It 
seems likely, in fact, that some of these rocks solidified within a few hundred feet of 
the surface. It is possible that the rocks into which they were intruded were then 
at a high temperature and that the cooling was consequently slower than it would 
otherwise have been. 

MINERALOGICAL CHARACTER. 

These syenites are in general made up of the same minerals as are the latite- 
phonolites. Analcite, however, is much less common, biotite is of more general dis¬ 
tribution, and pyroxene and hornblende are on the whole more abundant, though 
in the case of the latter mineral the difference may be due to the fact that prac¬ 
tically no resorption has taken place in these granular rocks. Nosean and sodalite 
are often present, but, as in the latite-phonolites, vary in amount and frequently 
can not be detected. 

Orthoclase is the most abundant constituent. It is usually present in individ¬ 
uals of irregular outline, but occasionally gives a subporphyritic texture to the rock 


86 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

by development in imperfect laths. Carlsbad twinning and visible traces of cleavage 
are less common than in the porphyries. Grains of microperthite are seen here and 
there. Plagioclase is rather abundant, and occurs like orthoclase. Polysynthetic 
twinning is often absent and the mineral must then be identified by its index, 
extinction, or double refraction. In composition it corresponds partly to albite 
and partly to oligoclase-albite, being thus a little more sodic than in the latite- 
phonolites. 

Kaolin, epidote, and sericite result from various processes of alteration of the 
feldspars. 

Nosean occurs as more or less automorpliic grains up to 0.6 mm. in size. It 
sometimes shows the characteristic grills of inclusions, but is commonly decomposed 
into a rather low polarizing aggregate of zeolites. 

Sodalite is often difficult of detection, but in a number of cases appears as 
minute grains between the other minerals, or more commonly included in the larger 
feldspars. In the neighborhood of mineral-bearing fissures sericite seems to form 
with particular ease from sodalite. 

Nepheline, if present at all, is in very subordinate amount and in no case could 
it be identified with certainty. 

Analcite has been found in a few instances as allotriomorphic grains along 
with the other constituents. In such cases it is undoubtedly primary. 

Pyroxene is one of the important constituents, and, aside from its somewhat 
greater abundance and generally poorer crystallographic form, its occurrence cor¬ 
responds to that in the latite-phonolites. It possesses on the whole the best form 
of all the important constituents of the syenites. It ranges from colorless, isochroic, 
to pale green, pleochroic, in the latter case indicating an admixture of a small 
amount of the segirine molecule. Twinning parallel to the orthopinacoid is seen in a 
few instances. A common alteration is to calcite, chlorite, and quartz(?). Other 
decomposition products occasionally seen are epidote, the secondary green mica 
alread} r described, sericite, and perhaps serpentine. 

The hornblende is of similar nature to that in the latite-phonolites, but differs 
somewhat in color. The range in color is as follows: a, light greenish yellow; b, 
yellowish green; c, deep green in some varieties, to a, brownish yellow; b, strong 
brown; c, deep greenish brown in others. In all cases c>b>a. The angle 
c:6 reaches a maximum value of 27°. Hornblende frequently shows poikilitic 
intergrowth with pyroxene and at times completely surrounds individuals of that 
mineral. In a few instances it is possible that slight resorption has taken place. 
Chlorite is a common alteration product. 

Biotite is rather common in irregular plates, usually of reddish-brown color, but 
sometimes greenish brown. Pleochroism is often intense. Like the mica of the 
porphyritic varieties, this mineral may be related to the iron-rich lepidomelane. It 
frequently occurs intergrown with hornblende and sometimes with pyroxene also. 
The most common decomposition product is aggregates of the secondary green mica. 

Apatite is present as numerous small, sometimes corroded, crystals and occa¬ 
sionally holds inclusions of the kind previously described. Titanite, while less 
abundant than in the latite-phonolites, is still of unusual prominence as an accessory. 
Small irregular grains of magnetite are common. 


TERTIARY VOLCANIC ROCKS-SYENITE. 


87 


As in the preceding-rocks, pyrite replaces magnetite, and carbonates and fluor¬ 
ite are introduced by metasomatic action along veins. 

The texture is in general typically granular, but occasionally becomes sub- 
porphyritic. The textural gradation to latite-phonolite has already been described. 

CHEMICAL CHARACTER. 


The analyses given below make clear the chemical nature of these rocks and 
their close relation to the latite-phonolites: 

Analyses of syenites from Cripple Creek. 


w 

I. 

II. 

III. 

IV. 

SiO;. 

54. 43 

54. 34 

51.98 

56.01 

A1 2 0 3 . 

19.01 

19.23 

17.94 

17.92 

FejOj. 

2.85 

3.19 

3.85 

4.20 

FeO. 

1.93 

2.11 

3.37 

2.52 

MgO. 

.99 

1.28 

2.88 

2.04 

CaO. 

4.33 

4.53 

5.62 

4.80 

Na 2 0. 

0.92 

6.38 

4.63 

4.92 

KjO. 

5.07 

5.14 

4.50 

4.21 

HjO —. 

.31 

. 14 

.72 

.31 

H 2 0+. 

1.68 

1.17 

2.09 

1.10 

Ti0 2 . . 

.96 

1.09 

1.34 

1.20 

ZrC >2 _ - . 

.04 

.07 

.03 

.02 

co 2 . 

.14 


Trace. 

Nor.e. 

P 2 0,. 

.25 

.27 

.67 

.55 

so 3 .. . 

.42 

.07 

None. 

None. 

Cl . 

.22 

.28 

Trace. 

Trace. 


.07 


.41 

.04 

MnO. . . 

.08 

.08 

.08 

.13 


.21 

.24 

.19 

.16 


.21 

.16 

.11 

.06 


Trace. 

Trace. 

Trace. 


* 1 

100.07 

99.77 

100.32 

100.19 


I. Latite-phonolite, south slope of Bull Cliff (IV of table on p. 79). 

II. Syenite, near Longfellow mine, west of Vindicator mine. See Cross, W., Sixteenth Ann. Rept. U. S. Geol. Survey, 


pt. 2, 1895, p. 45. 

III. Syenite, Portland mine, 500-foot level. 

IV. Latite-phonolite, Portland mine, 600-foot level (I of table on p. 79). 

Analyses I—III by W. F. Hillebrand; IV by George Steiger. 

II. This specimen is light gray and finely granular, with occasional larger 
grains of feldspar and numerous prisms of pyroxene showing a slight flow structure. 
In thin section the feldspars are found to be mostly ortlioclase, with some micro- 
perthite, considerable albite, and a little which is perhaps more calcic. Sodalite 
occurs in good-sized grains, some of them well crystallized, others of irregular form; 
it is commonly decomposed. The analysis indicates that a little nosean is also 
present. Analcite is rather plentiful in clear grains of irregular outline commonly 
associated with feldspar. Extremely minute needles, perhaps of stilbite, penetrate 
these grains. The occurrence of the analcite is the same as in the latite-phonolites. 
No nepheline can be distinguished, though Mr. Cross thought that certain turbid 
areas represent it. The pyroxene has the colors and low extinction angle of aegirine- 
augite. It is often surrounded by a zone of greenish-brown hornblende, which 


I 











































88 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

also occurs alone in good-sized individuals shoeing no resorption. Magnetite 
apatite, and titanite are notable accessory constituents. This rock, called nepheline- 
syenite in the earlier report, is regarded by Rosenbusch as a member of an inter¬ 
mediate series, the neplieline-syenite-essexite series.® It occurs not far from the 
locality of the latite-phonolite (I), which is compared with it on page 85, and it is 
probable that the respective masses of which these are specimens are connected 
underground. 

III. A rather light gray granular rock of moderately fine grain, holding well- 
formed prisms of pyroxene in a slightly pinkish aggregate of feldspar grains. Under 
the microscope the feldspar is found to range from orthoclase to oligoclase inclusive. 
A very little sodalite is present in tiny grains, and some larger areas, now converted 
into sericite, were possibly sodalite or nosean originally. The pyroxene is ver}" pale 
green and is practically isochroic, with an' extinction angle of about 40°. It is 
commonly accompanied by irregular grains of hornblende with pleochroism in light 
browns and greens, and by occasional small plates of strongly pleochroic biotite. 
Apatite is especially noticeable and is accompanied by magnetite and titanite. 
The texture is hypidiomorphic granular. This specimen and No. IV of the table 
on page 87 are from the Portland mine, and though from different masses are strik¬ 
ingly similar in chemical composition. 

TRACHYDOLERITE (BULL CLIFF TYPE). 

GENERAL DESCRIPTION. 

The summit of Bull Cliff is made up of a dense, nearly aphanitic rock, almost 
black in color, which after partial weathering gives a peculiar rough fracture as if it 
were made up of polyhedrons. It was thought by Cross to grade into normal 
phonolite to the south and to be a peculiar local facies of that rock. While later 
field study has not been able to wholly establish its geological relations, there are 
certain facts which lead to a rather different view. The summit mass is on the 
whole very fresh, while most of the true phonolite to the south is much decomposed. 
The freshest of the near-by phonolite shows the fissility, the greasy luster, the 
tablets of feldspar, and the flow structure of the type, while the rock from the 
summit possesses none of these characteristics, but occasionally shows a very small 
glistening phenocryst of mica. There seems to be no gradation in appearance near 
the boundary between the two rocks and while talus and low scrubby bushes con¬ 
ceal the actual contact it is beyond question that an intrusive contact is present. 
The Bull Cliff mass overlies and is later than the breccia. On the west side of the 
hill the contact is nearly horizontal. On the east side it dips into the hill at some¬ 
thing like 45°. Workings in the Isabella and Victor mines directly underneath 
the cliff do not encounter this rock, so far as known, but it is probable that it has 
issued from some small throat and spread out into the surrounding rocks as a 
laccolith-like mass. A rude vertical columnar jointing on the east side favors this 
view. The rock is younger than the latite-phonolite, for it is seen cutting off a 
dike-like body of that rock in the Pilgrim tunnel on the northwest slope of Bull 
Cliff. From such field evidence as can be obtained, which, it must be admitted, 
is not entirely convincing, it appears to be later than the phonolite. 


a Elemente tier Gesteinslehre, Stuttgart, 1901, pp. 177, 179. 








TERTIARY VOLCANIC ROCKS-TRACHYDOLERITE. 


89 


Microscopical and chemical study shows that this rock belongs in Rosen- 
husch’s family of trachydolerites, which are defined as containing in a fine-grained 
groundmass phenocrysts of generally calcic plagioclase and of pyroxene, and often 
accompanied by sanidine, a mineral of the sodalite group, hornblende, and olivine. 

MINERALOGICAL CHARACTER. 

The essential minerals of this rock are orthoclase, plagioclase, pyroxene, 
biotite, and analcite, with abundant black iron ore and many crystals of apatite 
as accessories, and here and there a little glass. 

Phenocrysts of feldspar rarely exceed 0.5 mm. in greatest dimension and are 
always triclinic, belonging to the variaties oligoclase and andesine. Twinning is 
common and cleavage is particularly evident. Aside from prominent clinopina- 
coids, crystal faces are not well developed. 

Feldspar of the second generation is about equally divided between orthoclase 
and plagioclase the latter including albite, oligoclase, and andesine. They are 
usually developed as laths, as in the trachytes, but are often of irregular form. 

Pyroxene is very abundant, both as phenocrysts reaching 0.3 mm. in size, often 
anhedral, and as small lath-shaped microlites profusely scattered through the 
groundmass. The mineral is colorless or very pale yellowish-green and without 
noticeable pleochroism. The interference colors are moderate and the angle of 
extinction is large. The optical properties and the composition of the rock make 
it probable that this pyroxene is related to augite. 

The manner of occurrence of biotite is rather unusual. It forms small ragged 
grains of brown color and intense pleochroism and is closely associated with grains 
of iron ore. Elongated individuals of larger size, sometimes 2 to 3 mm. in length, 
show what is probably an unusual kind of resorption. Small grains of black iron 
ore, pyroxene, and a colorless mineral—probably feldspar—mingle throughout the 
mass with residual particles of the biotite still retaining the original orientation. 
At times the pyroxene grains arrange themselves according to crystallographic 
directions, and then the pyroxene and biotite individuals possess the vertical axis 
in common. The pyroxene resulting from the magmatic alteration of biotite 
appears to be identical in composition with the original pyroxene. 

Analcite occurs in variable amounts, as rounded patches 1 mm. or more in 
diameter, and more commonly as irregular interstitial grains between the other 
groundmass constituents. When in the larger patches, it holds abundant laths of 
pyroxene and feldspar arranged in the same parallel fluidal way as in the other 
parts of the rock. The mineral is uniformly colorless and clear, shows the low 
single refraction and characteristic rough surface, and is sensibly isotropic, though 
small areas of exceedingly faint polarization are occasionally seen. The possibility 
of this material being glass, as its occurrence suggests, is almost wholly excluded by 
its clearness and freshness in a rock which carries over 1 per cent of carbonate. No 
question can be raised, on the other hand, as to the primary character of the analcite. 

Apatite is common in crystals which range in size from very minute up to 
0.3 mm. They are nearly always crowded with the acicular inclusions described 
under the latite-phonolites, and consequently present a very striking pleochroism 
in brown and purple. 


90 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

Black iron ore is very plentiful, and in the absence of spliene must be titaniferous 
to a considerable extent. (See analysis.) 

Small interstitial particles of turbid appearance and brown color occur scattered 
sparingly through the groundmass. They possess weak single refraction and give 
aggregate polarization in low colors, and without doubt are devitrified portions of 
an original glass bases. 

The texture of this rock is therefore hypocrystalline porphyritic. The holo- 
crystalline portions are generally intermediate in character between the trachytic 
texture of the phonolites and latite-phonolites, and the intersertal texture of the 
basalts. Small portions of the groundmass are microgranular. 

CHEMICAL CHARACTER. 


The composition of this rock is shown in the analysis, by Hillebrand,® given 
below. 


Analysis of trachydolerite from Bull Cliff. 


Si0 2 .. 
AhOj . 
Fe 2 0 3 . 
FeO.. 
MgO . 
CaO.. 
Na 2 0 . 

k 2 o.. 

h 2 o- 

H„0+ 
Ti0 2 . 


49.84 

ZrO z 

17.78 

co 2 . 

5.86 

PA 

2.62 

so 3 . 

3.02 

CL. 

7.35 

MnO 

5. 20 

BaO 

3.04 

SrO. 

.34 

Li 2 0 

2.02 


1.43 



.03 
.52 
. 76 
None. 
Trace. 
.21 
.22 
. 18 
Trace. 


100 . 42 


A comparison of this analysis with No. Ill on page 87 reveals the close chemical 
relation of the trachydolerite with the less alkalic of the syenites. 


SUMMARY. 

The occurrence of analcite as a groundmass constituent in a role similar to 
that of glass places this rock in Pirsson’s “analcite group,” 6 along with the mon- 
chiquites which it somewhat resembles/ 

From what has been said of its field occurrence and of its mineral and chemical 
composition, it appears probable that this trachydolerite is intermediate in age as 
well as in character between the latite-phonolites and syenites, on the one hand, 
and the latest products of eruption, the basic dike rocks, on the other. 

BASIC DIKE ROCKS. 


GENERAL DESCRIPTION. 

Cutting all the other rocks of the district, and hence representing the final 
phase of eruptive activity, are certain dark intrusives which occur as dikes and sills 
from a few inches to several feet in thickness. They are most abundant in the 


a Bull. U. S. Geol. Survey No. 228, 1904, p. 163. 

b On the monchiquites or anabite group of igneous rocks: Jour. Geol., vol. 4, 1896, pp. 679-690. 
c Cross, W., Sixteenth Ann. Rept. U. S. Geol. Survey, pt. 2, 1895, p. 37. 

























TERTIARY BASIC DIKE ROCKS. 


91 


volcanic rocks, but occasionally cut the granites. As in the case of the phonolites, 
there is seen a tendency toward radiation from the center of the eruptive area. 
When fresh they are nearly or quite black rocks, with conchoidal fracture, and vary 
in granularity a from fine-grained porphyritic to aphanitic. Their mineralogical 
composition is such that they readily undergo alteration and with the exception of 
the northeasterly dike which outcrops in the main street of Altman they are not 
conspicuous at the surface. This decomposition is not limited to the vicinity of the 
surface, but frequently extends to depths of over 1,000 feet, changing the rock in 
extreme cases to a soft and clayey greenish-gray crumbling mass, while less decom¬ 
posed portions vary from light to dark gray or greenish and are more or less porous 
through the removal of some of the constituents. 

These rocks are locally known as basalts and have usually been mentioned as 
such in the literature. On the basis of partially decomposed material, Cross 
made two divisions which he called plagioclase basalt and nepheline basalt, respec¬ 
tively. To these Stevens added limburgite* and tephrite. c Careful examination 
of specimens collected from all parts of the district establishes three definite rock 
types which while outwardly resembling basalts are because of their notable 
content of alkalies really not basalts at all. They are trachjMolerite, vogesite, 
and monchiquite. For various reasons it has been found impracticable to separate 
them on the map, where they appear as “basic dikes.” In order to distinguish the 
first-named type from the rock of Bull Cliff, it will be designated as the Isabella 
trachydolerite. 

TRACHYDOLERITE (ISABELLA TYPE). 

This group is exemplified by the dike in the Isabella mine, which can be traced 
through the town of Altman nearly to the summit of Bull Hill and extends north¬ 
ward through the Block 8 mine to Grassy Creek. It is also represented by the 
Dolly Varden dike, by a dike crossing the Gold Bond property, one in the Ajax 
mine, and several in the Portland mine, and by an inclined dike in the Mary 
McKinney mine. Several dikes, such as those in the Blue Bird and Midget mines, 
though much decomposed, probably also belong to this type. 

These rocks are distinctly phanerocrystalline, but of fine grain, and consist of 
plagioclase, pyroxene, and olivine, with smaller amounts of orthoclase and analcite, 
with or without a glass basis. As accessory or occasional constituents, occur apatite, 
magnetite, biotite, and hornblende. The plagioclase ranges from andesine to 
bytownite, inclusive, and though more than one species is sometimes contained in 
the same specimen, labradorite is most common. It occurs in tabular plates, but 
more frequently as laths, from over a millimeter in length down to minute microlites. 
It is seldom more than hypidiomorpliic, but in a few cases attains almost perfect 
form. It occurs at times only as phenocrysts, at others both as phenocrysts and 
in the groundmass, while not infrequently it is confined wholly to the groundmass. 
Arrangement in zones of not very different composition may often be observed, and 
occasionally the phenocrysts are surrounded by a narrow, irregular, clear zone of 

a Quantitative Classification of Igneous Rocks, Chicago, 1903, p. 154. 
b Trans. Am. Inst. Min. Eng., vol. 30, 1901, pp. 759-764. 
c Idem, voi. 33, 1903, p. 687. 





92 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


orthoclase. Twinning, though not always present, usually follows the albite law 
and sometimes the Carlsbad law also. Pericline twinning is rarely seen. In some 
cases small patches of turbid glass are inclosed in zonal arrangement by' the feldspar 
phenocrysts. Orthoclase is not ver} T abundant, occurring, with the exception of the 
Outer shell of the plagioclase phenocrysts, as small interstitial grains. Analcite is 
present in phenocrystic individuals which in thin section have an approach to 
square or hexagonal outline. It also occurs as rounded blebs, sometimes inclosing 
or penetrated by prisms of pyroxene, and as irregular interstitial grains. A com¬ 
mon alteration is to radiating needles of stilbite. Augite occurs as phenocrysts, 
generally characterized by good crystallographic form, and also as more or less 
irregular grains in the groundmass. Cleavage is noticeably developed. Besides 
the usual prismatic cleavage, there is a prominent cleavage parallel to the clino- 
pinacoid, and sometimes ortliopinacoidal and negative orthodomal cleavage. The 
phenocrysts not infrequently show twinning parallel to the orthopinacoid and zonal 
structure is almost always present. Small particles of glass are sometimes included 
near the periphery of the larger individuals. In one rock, at least, that from a dike 
near the Gold Bond mine, corrosion and subsequent enlargement of the pyroxene 
individuals have taken place. The mineral is usually colorless or very light green. 
In one or two instances it shows a faint purple tint, indicative of the presence of 
titania, and then possesses a slight pleochroism. Olivine occurs as large and small 
phenocrysts, more or less idiomorphic, and sometimes as small graips in the ground- 
mass. When fresh, it shows the usual irregular cracks along which alteration begins 
and in certain instances shows an imperfect cleavage also. Generally it is in an 
advanced stage of alteration, the more common and noticeable products being car¬ 
bonates, serpentine, talc, and a material corresponding to what has been called 
iddingsite. ° Biotite occurs rarely as phenocrysts, but is comparatively abundant 
in the groundmass as small grains, usually reddish brown, intensely pleochroic, and 
with high interference colors. It sometimes shows both corrosion and resorption. 
Hornblende occurs sparingly as irregular individuals of brown color. A dike in the 
Ajax mine contains a weakly pleochroic bluish-green amphibole. The apatite, 
which occurs in prisms as much as 2 mm. in cross section, is particularly free from 
inclusions. 

In two of the rocks of this type a few' grains of obviously secondary quartz are 
found. Epidote is rather plentiful in some of the partially decomposed specimens 
and carbonates are nearly always abundant. 

These rocks possess a texture which is about midway between trachytic and 
intersertal. Most of them appear to be holocrystalline, but some undoubtedly 
contain small areas of brown, turbid glass. 

A chemical analysis of material from the Isabella dike w 7 as made by W. T. 
Schaller, and serves to show the alkalic nature of the rock and its close relation to 
the trachydolerite of the Bull Cliff mass. 


a Lawson, A. C., Bull. Dept. Geol. Univ. California, vol. 1, p. 31. 



TERTIARY BASIC DIKE ROCKS. 


93 


510 2 .. 
A1 2 0 3 . 
Fe 2 O s . 
FeO.. 
MgO.. 
CaO.. 
Na 2 0. 
K 2 6.. 
H,0— 

11.. . 0 + 
TiO z .. 
Zr0 2 .. 


Analysis of trachydolerite of the Isabella dike. 


48.76 

C0 2 .. 

17.04 

p 2 o 5 . 

5. 04 

so 3 .. 

3. 47 

Cl... 

4.57 

FeS 2 . 

8. 64 

Cr 2 0 3 

4. 27 

MnO. 

3. 39 

BaO. 

.69 

SrO.. 

1.84 

1.34 

Trace. 

Li 2 0. 


0. 22 
.79 
Trace. 
.01 
. 11 
Trace ? 
.08 
. 15 
.07 
Trace. 


100.48 


A subtype of this group is represented in two dikes southeast of the Eagle mine 
on Bull Hill. They differ from the preceding rocks mainly in holding no olivine. 
On the other hand, their texture, which is intersertal, relates them more closely to 
the basalts. A decomposed rock occurring as a dike in the Ophelia tunnel probably 
belongs here. 

VOGESITE. 


The rocks of the vogesite group are phanerocrystalline, but are generally of 
fine grain. Small rounded grains of light-colored material (analcite) and flakes of 
dark mica are the characteristic minerals of the hand specimen. The rock of the 
Anna Lee dike in the Portland mine contains mica plates up to 1 cm. in diameter. 
Besides the Anna Lee dike, the dike in the Moose mine, one in the Jennie Sample 
mine, the Pinto dike, and perhaps some others are of this type. 

The microscope shows the essential constituents to be orthoclase, hornblende, 
pyroxene, and biotite, with usually some analcite, frequently olivine, and at times 
a little plagioclase. The monoclinic feldspar is abundant as rather irregular laths 
of good size, usually untwinned. Plagioclase is only sparingly present and 
from its low, double refraction is probably albite. Analcite occurs in octagonal 
phenocrysts, also as rounded amygdule-like grains and as groundmass areas, as in 
the Bull Cliff rock. On decomposition it forms stilbite and is sometimes replaced 
by sericite. Brown hornblende is plentiful in long columns bounded by prism, 
clinopinacoid, and orthodome faces. It is often twinned. The pleochroism is not 
very strong. Augite is rather abundant in crystalline grains and a few larger 
phenocrysts. Numerous small foils of deep-brown mica are present. Olivine was 
present in considerable amount, but is now largely changed to serpentine and car¬ 
bonates. Apatite is not common, but shows the same inclusions as in the Bull 
Cliff trachydolerite. Small particles of black iron ore are scattered here and there. 

While the size of the individuals of the several constituents is not uniform and a 
porphyritie appearance sometimes thereby results, the rocks are essentially 
panidiomorphic granular in texture. 

The analysis given below reveals the chemical similarity to the trachydolerites of 
the Isabella and Bull Cliff types. It shows that these rocks are somewhat deficient 
in ferromagnesian and rich in alkalic constituents for the typical vogesite, but the 
discrepancy is not very great and mineralogically they agree very closely. 

13001—No. 54—06-8 


























PLATE IX. 

Photomicrographs of Rocks. 

A, Tracliydolerite (661 C. C.) from Isabella mine, level 10. Composed of orthoclase, plagioclase, analcite 

augite, olivine, and magnetite. Orthoclase and analcite are confined to the groundmass. Magnified 
28 diameters. 

B, Monchiquite (204 C. C.) from dump of Block 8 mine. Composed of analcite, augite, olivine, with a small 

amount of orthoclase. Analcite in phenocrvsts and orthoclase in the groundmass. Magnified 28 
diameters. 

C, Vogesite (569 C. C.) from Jennie Sample mine, level 5. Composed of orthoclase, analcite, hornblende, 

and biotite. Magnified 35 diameters. 

94 




U. S. GEOLOGICAL SURVEY 


PROFESSIONAL PAPER NO. 54 PL. IX 



A B 



C 

PHOTOMICROGRAPHS OF TRACHYDOLERITE, MONCHIQUITE, AND VOGESITE. 















TERTIARY BASIC DIKE ROCKS. 


95 


Analyses of vogesite. 


SiC>2.. 

AI2O3. 

Fe 2 0 3 . 

FeO.. 

MgO. 

CaO.. 

Na20. 

K 2 0.. 

HjO- 

H s O+ 

TiOj.. 

ZrC> 2 . 

CO s .. 

P 2 O 3 .. 


I. 

II. 


I. 

II. 

47.31 

45.15 

so 3 . 

0.05 


16.21 

15.39 

Cl. 

.05 


5.05 

2.76 

FeS 2 . 

. 12 


2.90 

5.64 

Cr 2 0 3 . 

Trace. 


3.08 

6.38 

MnO. 

Trace. 

.14 

7.11 

8.83 

BaO. 

. 17 


3.92 

2.67 

SrO. 

.02 


3.73 

2. 77 

Li 2 0. 

Trace. 

Trace. 

87 





2.17 

2.85 


100.29 

100.21 

1.64 

2.80 

Less O for Cl. 

.01 


.01 



100.28 


4.98 

4.27 




.90 

.56 





I. Vogesite, Jennie Sample mine, Cripple Creek. W. T. Schaller, analyst. 
II. Vogesite, Castle Mountain. Bull. U. S. Geol. Survey No. 134, page 112. 


MONCHIQUITE. 

The monchiquites vary in granularity from aphanites to fine-grained por¬ 
phyries holding phenocrysts of dark pyroxene'", red olivine, and white amygdule- 
like grains of analcite. One specimen from a dike in the Gold Sovereign mine, has 
numerous flakes of dark biotite. Dikes referable to this group are known in many 
places, as in the Mollie Kathleen, Pointer, Gold Sovereign, Vindicator, Block 8, 
Ajax, Granite, Portland, and Strong mines, and in the Ophelia and Raven tunnels. 
A decomposed rock in the Ida May mine probably belongs here. 

The characteristic of this group is the presence of abundant phenocrysts of 
pyroxene and olivine embedded in a matrix of analcite. Orthoclase is not uncom¬ 
mon as small grains in the groundmass, and albite occurs sparingly in a similar 
manner. Analcite occurs in round grains of a millimeter or two in size, penetrated 
by and inclosing crystalline grains of pyroxene. It often shows the characteristic cubic 
cleavage and faint shadowy birefringence. In a few instances these areas of analcite 
contain minute crystalline grains of a clear and colorless mineral of slightly higher 
refractive index than analcite and a double refraction of about 0.001 or 0.002. 
They appear to be made up of several hexagonal plates partially merged. It seems 
possible that the mineral is a zeolite, and if so it may be gmelinite, with which it 
corresponds closely. That it is leucite is remotely possible. Analcite also occurs 
very evenly distributed throughout the rock as a matrix for the other constituents, 
but relative to the amount of pyroxene and olivine it is not abundant. In this 
mode of occurrence it resembles the material in the larger areas, being clear and 
colorless, of so low index that the surface appears rough, and occasionally showing 
faint polarization. In both cases the material is easily decomposed to a some¬ 
what turbid mineral, mostly developed in slender laths, which has properties 
corresponding to stilbite. Owing to the readiness with which analcite is dissolved, 
it is frequently partially replaced by dolomite. The pyroxene is probably augite 
and occurs in phenocrysts of two generations. The older individuals vary from 





















































96 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

0.3 to 0.8 mm. in size, while the more abundant younger grains range from 0.2 mm. 
down. Practically no difference can be distinguished in the character of the two 
generations. Many of the olivine grains possess excellent form, but some are of 
irregular shape. They vary in size from 0.1 to 1 mm. Serpentine, carbonates, 
and iddingsite are the common alteration products. Biotite is of common occur¬ 
rence in the groundmass. The biotite of the Gold Sovereign dike is yellowish red, 
pleochroic to nearly colorless, and gives brilliant interference colors. A few small 
crystals of apatite and many small grains of magnetite are present as accessories. 

In texture these rocks are analogous to liypocrystalline-porphyries in which 
analcite is present instead of glass. 

Chemically they are richer in alkalies than many monchiquites, as an analysis 
shows. But, on the whole, they correspond very well with that group and better 
than with any other. 

Analyses of monchiquites. 



I. 

II. 


I. 

II. 

Si02.-. 

44.08 

43. 74 

Cl. 

0.04 

Trace. 

AI 2 O 1 . 

12.80 

14.82 

FeS 2 . 

.26 


4.58 

2. 40 

S. 

.10 

FeO. 

3. 72 

7.52 

Cr 2 0 3 . 

.05 

MgO. 

7.22 

6.98 

MnO. 

. 14 


CaO. 

11.21 

10.81 

BaO. 

. 13 


Na 2 0. 

2.97 

3.06 

SrO. 

.06 


K 2 0. 

3.31 

2.90 


Trace. 


H 2 O-. 

H 2 O 4 -. 

. 77 

2.35 

| 2.94 


99.97 

100. 23 

Ti0 2 .’. 

1.43 

2.80 

Less O for Cl. 

.01 


C0 2 . 

P 2 O 5 . 

SO 3 . 

4.14 

.70 

.01 

1.50 

. 64 


99.96 



I. Monchiquite, Block 8 mine, Cripple Creek. W. T. Schaller, analyst. 

II. Monchiquite, Rio do Ouro, Brazil. Rosenbusch, Elemente der Gesteinslehre, Stuttgart, 1901, p. 244, analysis 8. 


It was evidentlv this class of rocks which Stevens called limburgites. In his 

«y ~ 

description it will he noted that Kemp, who made the determination, spoke of the 
plienocrysts as present in “a clear, colorless, isotropic base, either glass or anal¬ 
cite.” “ If the base were glass, the rocks would be limburgites, but since it is 
analcite they belong with the monchiquites of Pirsson.*' 

The dike from near the end of the Raven tunnel belongs to the same series of 
intrusions and is probably composed of a rock of similar character to that which 
Cross collected from the Appie Ellen shaft and which, from the analysis on page 50 
of the 1894 report, lie calls a nepheline basalt. He notes that the rock was con¬ 
siderably decomposed and that treatment with cold dilute hydrochloric acid dis¬ 
solved nearly all of the soda. It seems quite probable that the soda was carried 
not by nepheline but by analcite and its decomposition products, like stilbite, 
especially since Cross’s determination of nepheline by the microscope was not very 
positive. 


a Trans. Am. Inst. Min. Eng., vol. 30, 1900, p. 763. 


b Jour. Geol., vol. 4, 1896, pp. 679-690. 






















































TERTIARY VOLCANIC ROCKS-BRECCIA. 


97 


SUMMARY. 

Nothing of very general application can be stated regarding the relative age of 
these three classes of dikes. In the Pinto mine the intersection of the Isabella 
and Pinto dikes is shown, and though, owing to the nature of the workings, a final 
opinion can not he reached, apparently the larger (Isabella) dike cuts and is there¬ 
fore younger than the northward-trending Pinto dike. In the Block 8 mine a 
large dike which corresponds in every way to the Isabella dike cuts and faults the 
smaller monchiquite dike. Whether or not other dikes of the same respective 
classes are contemporaneous with these was not determined. On the assumption 
that they are, it may be said that the Isabella trachydolerite is younger than either 
the vogesite or the monchiquite, but no evidence has been found as to the relative 
age of the last two. 

The foregoing descriptions make it plain that there are marked mineralogical 
and textural differences in these three groups of rocks. The analyses, on the other 
hand, show that the rocks are very closely related chemically and that they differ 
scarcely more from one another than they do from other rocks in the classificatory 
division in which they have been placed. For this reason the names assigned to 
them are not wholly satisfactory, but nevertheless seem to be the best now in use. 
It is possible that analyses of other specimens would show what is suggested by 
some of the thin sections—a still closer chemical relationship between the three 
groups and perhaps a complete gradation from one extreme to the other. 

Finally, these basic dike rocks as a whole show close relationship to the type 
just preceding, the Bull Cliff trachydolerite, and through it are connected with all 
the foregoing Tertiary rocks. They complete, in the order recognized as normal, 
the series of eruptions from the Cripple Creek volcano. 

BRECCIA. 

The pyroclastic or fragmental volcanic rocks of the district have an extensive 
development. The largest area is a rude ellipse with the longer axis extending 
about 4 miles in a northwest direction from just north of the summit of Big Bull 
Mountain to the pass between Carbonate and Tenderfoot hills. The greatest 
width is about 2\ miles, reaching from the west side of Guyot Hill to Grassy Creek 
at Cameron. Masses of considerable size occur on Mineral Hill and Rhyolite 
Mountain, and smaller bodies are found on Copper Mountain, east of Galena Hill, 
on the summit of Big Bull Mountain, and on the upper part of Mount Pisgah just 
west of the area covered by the map. 

The fragmental character of these rocks is generally discernible with readiness. 
They are, moreover, wholly fragmental, and do not consist, as is often the case, 
of numerous fragments held in a matrix which solidified about them from the 
molten state. They are made up of angular pieces which are, on the average, equi- 
dimensional and which vary in size from very minute grains to blocks over a meter 
in diameter. The name “ breccia ” is here applied to all these rocks, though “ tuff ” or 
“agglomerate” are in some cases more appropriate terms. There is usually no 
assortment of the material, and coarse and fine pieces occur together. The variety 


98 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


most commonly met with consists of fragments whose maximum size is 2 to 3 
cm., in a more finely granular matrix. In some cases all the grains are of small 
size, and then the true clastic nature of the rock is not always easily detected. 
Occasionally, however, a distinct banding is apparent, the material being well 
assorted into even layers a millimeter or less in thickness of extremely fine mate¬ 
rial, alternating with layers sometimes several centimeters thick of coarser yet 
still very small particles. Bedded tuff of this kind is seen on the slope north of 
Altman, at the southwestern base of Bull Cliff, and in the Lucky Guss No. 2 and 
Portland mines. In some cases the bedding is nearly or quite horizontal; in others 
it is much inclined. The appearance of some of this bedded tuff suggests that it 
is a deposit in quiet water. 

All these rocks are considerably altered, even at the greatest depths attained 
in the mines. The freshest are soft, not very compact, of reddish, purplish, or 
bluish-gray color. Slight weathering changes them to brownish, probably by 
conversion of the iron into limonite. Most of the rock appearing at the surface 
has a light-yellowish color and is compact, owing to decomposition by atmospheric 
agencies. Hydrometamorphism, however, has been only one factor in the altera¬ 
tion of these rocks. Impregnation by dolomite and pyrite is a very common 
feature and may be attributed to the action of gases and solutions emanating 
from the seat of the Cripple Creek volcano. Small crystalline grains of pyrite or 
characteristic little cavities which lesult from its oxidation frequently serve to 
distinguish fine-grained, decomposed breccia from massive latite-phonolite. When 
rock thus heavily pyritized is exposed on a dump to the action of the atmosphere 
it frequently swel s, cracks, and crumbles to a greenish-yellow powder. 

Near the contact with granite and with schist the breccia generally contains 
a greater or less proportion of those rocks or of their constituent minerals. But 
the presence of these materials is uncommon in the great mass of the breccia. It 
appears, therefore, that the ancient crystalline rocks which occupied what is now 
the throat of the volcano were shattered and thrown out of the opening by violent 
explosions. 

Cross, judging from specimens generally much decomposed, was of the opinion 
that the breccia is made up largely of andesitic rock. The extensive mine work¬ 
ings now give much additional information as to the character of these fragmental 
materials. In spite of the alteration which it has suffered, an examination of the 
breccia shows that it is made up chiefly of phonolite and latite-phonolite. The 
abundance of phonolite fragments in the breccia and the sharp contact of the 
massive phonolite with it prove that there took place at least two phonolite intru¬ 
sions of considerable magnitude. But with the latite-phonolite the case appears 
to be different. Sharp contacts with the breccia do appear, it is true, as in the 
Trail tunnel, but in general the massive rock passes, by a gradual increase of shat¬ 
tering, into true breccia composed of various materials. In several places, as on 
the northeast knoll of Battle Mountain, the latite-phonolite is simply crushed and 
the fragment^ are only slightly dislocated. At increasing distance from the massive 
rock the disturbance becomes greater and the derangement of the grains finally 
admits the mingling of foreign fragments. In many places, particularly on the 
western slope of Bull Hill, an intermediate stage of this shattering has resulted 


TERTIARY VOLCANIC ROCKS-BRECCIA. 


99 


in a true breccia, composed, however, almost exclusively of fragments of latite- 
phonolite. 

Granite (or schist or gneiss) brecciated in place in a similar manner occurs 
in narrow zones at several places along the contact, and in larger areas on the 
southern slopes of Carbonate and Mineral hills. The material is almost exclu¬ 
sively granite, with a rare fragment of volcanic rock. The grains are angular and 
appear to have suffered little dislocation. Only careful examination distinguishes 
this rock from massive granite, into which it grades. Its presence in considerable 
amounts at the northern edge of the main area seems to indicate that violent 
forces were at work at that place, but that they were not sufficient to wholly 
remove the shattered material, as was done in other places. This brecciated granite 
is not to be confounded with breccia, like that near the summit of Mineral Hill, 
composed largely of granite fragments which are not so strictly of local derivation. 
Granitic breccia of this kind is more or less loose and shows a sharp contact with 
the massive granite. 

Fragments of vesicular, glassy rock have been found in some of the outlying 
breccia areas—for instance, in the small mass near the southwest corner of the 
area mapped and in one specimen from Copper Mountain. No material of this 
kind has been found in the main breccia mass, though the great decomposition 
which this fragmental rock has in many places undergone makes it impossible to 
speak with certainty on this matter. 

On the dump of Stratton’s Independence No. 2 shaft occur a few blocks of 
interesting material. It is a fine-grained, structureless tuff of light color, some¬ 
what dolomitized, holding numerous small round pellets, nearly white, and var} T ing 
from 1 to 6 or 8 mm. in diameter. Many of these have, instead of a single curved 
surface, a botryoidal or mammillary form, suggestive of concretions. When these 
are broken it is seen that a thin shell incloses material similar to that of the main 
portion of the rock. A thin section containing one of these pellets shows that 
the shell is made up of the same materials as occur both outside and inside of it, 
only of much finer grain. The interior of the globule seems to hold more carbonate 
than the material outside. 

Whether these globules represent accumulations about drops of water,® and 
hence indicate the presence of surface conditions, or whether they have been 
formed by concretionary depositions from perhaps carbonated waters, and hence 
may have originated at a distance from the surface, it seems impossible to decide. 

The microscope confirms the conclusions reached from an examination in the 
field. With the exception of the fragment of leucitophyre already described and 
the few occurrences of vesicular rock mentioned above, not a single mineral or 
particle of original material was seen in the scores of thin sections of breccia exam¬ 
ined which is not represented in known areas of massive rock occurring in the 
district. The most prominent constituent is phonolite, usually in fragments which 
show only the trachytic groundmass, but occasionally phenocrysts are seen. But 
little less abundant are similar fragments of latite-phonolite. Next in abundance 
are broken phenocrysts of fyddspar from these tWo rocks. Grains of magnetite 
from the latter are also common in some specimens. Broken grains of quartz, 

“Cl. Howe, Ernest, Recent tuffs of the Soufri&re, St. Vincent: Am. Jour. Sei., vol. 16, 1903, pp. 319-320. 





100 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

microcline, and orthoclase are frequent and sometimes very plentiful, and locally 
fragments of schist are seen near the contact, but rarely in the midst of the breccia 
body. Sometimes the rock is evenly granular, but more commonly the larger grains 
are held in a finer-grained groundmass. which is at times so comminuted that the 
highest powers of the microscope detect individual grains only with difficulty. The 
feldspars show some kaolinization, but are otherwise usually little changed. Dark 
silicates of all kinds are almost entirely removed through decomposition, and their 
place is frequently taken by either carbonate or pyrite, which also replace other 
minerals. Practically every specimen holds considerable dolomitic carbonate, and 
it proves to be this mineral which has accomplished most of the cementation and 
induration. A few grains of secondary quartz and chalcedony are sometimes 
observed, and little patches and microbotryoidal concentric coatings partially filling 
cavities are composed of opal. Silicification is, on the whole, however, surprisingly 
slight. The great majority of specimens hold crystalline grains of pyrite formed by 
replacement. Fluorite is found sparingly distributed throughout most of the 
breccia in small grains which have replaced other constituents. In the vicinity of 
mineral veins silica, carbonate, fluorite, and pyrite are apt to be more plentiful. 

RHYOLITE. 

Exposed in small isolated patches on the upper slopes of Grouse Hill is a vol¬ 
canic rock readily determined as rhyolite. To the west of the Cripple Creek district 
the rock occurs in much larger areas which were doubtless originally connected 
and formed an extensive sheet. It is probable that this was largely a surface flow. 
It is considered by Cross to be of Miocene age. Where freshest the rock is cf 
brownish-red color and composed of a compact, earthy groundmass, in which occur 
a few small crystals of sanidine and still less numerous grains of quartz and glisten¬ 
ing flakes of biotite. None of the phenocrysts exceed a size of over 3 mm. In 
most places the rock is bleached to a light yellow and exhibits a noticeable vesicular 
structure which shows the direction of flow. In this weathered condition the 
rhyolite is easily mistaken for the fissile, bleached phonolite which occurs near by. 

Quartz occurs in clear fragmental grains, frequently corroded and often holding 
embayed areas of the groundmass. Many of the phenocrysts of sanidine are well 
formed, and they commonly show Carlsbad twinning. Some of them are likewise 
corroded. A comparatively small amount of microcline is present. Biotite occurs 
in brownish foils, but is frequently decomposed and removed. The predominant 
groundmass is evidently a partially devitrified glass rich in silica. It shows the 
peculiar patterns of the felsophyric texture. In the more decomposed specimens 
the crystallization of the originally amorphous basis has reached such a stage that 
the groundmass may be called microgranular. 

Cross considered that the rhyolite was older than the feldspathic grits of Grouse 
Hill and Straub Mountain, and on this conclusion based his arguments concerning 
the age of the Cripple Creek volcano. Later study has necessitated some modifi¬ 
cations of this conclusion. It now seems probable that the grits have been invaded 
by the later rhyolite and indurated near the contact. The presence of rhyolite in 
them may be explained by brecciation at the time of intrusion. That brecciation 
of the rhyolite has actually occurred can be seen at one place. The contact of 


PETROLOGY OF THE DISTRICT-GRANITE GROUP. 


101 


rhyolite and grits is at nearly every place a sharp and close one. The rhyolite at 
the contact appears to be no more weathered than elsewhere, but it does show a 
narrow zone of finer, denser texture in immediate contact with the grits. The flow 
structure is parallel to this contact. In many places the upper part of the rhyolite 
is broken and cracked, and the fragments are angular. While the grits appear to 
have been in most places unconsolidated at the time of the intrusion and have fallen 
down into cracks and between fragments of the rhyolite, in a few cases the rhyolite 
seems to have broken across some of the mineral grains of the grits. There are 
indications just south ot the boundary of the area shown in the map and also on the 
top of Grouse Hill that the grits partly underlie the rhyolite. Therefore, while final 
proof is perhaps lacking, it seems almost certain that the rhyolite is younger than 
the grits. 

PETROLOGY OF THE DISTRICT. 

In the foregoing pages of this chapter an endeavor has been made to present 
the distribution and the petrographic and chemical character of the various igneous 
and metamorphic rocks which occur within the Cripple Creek district. Short 
summaries have been given of the prominent features of the best-defined types, 
and in some cases a few words have been devoted to showing relations between 
certain of these types. It is the intention in the present section to view these 
rocks more broadly by considering them as products of crystallization from magmas. 
It will be the aim to hold closely to the facts as shown by the field occurrences 
and by the microscopic and chemical investigations and to avoid such considerations 
of the origin of the rocks, magmatic differentiation, and the like, as are purely 
theoretical. 

For this purpose it will be advisable to disregard the gneisses and schists, in 
which metamorphism has been so intense that their origin is largely a matter of 
conjecture. The rhyolite, also, will not be considered, as it came from an extrane¬ 
ous source and is in no way essentially related to any of the other rocks of the 
district. The remaining rocks are igneous and may be divided on the grounds of 
magmatic relations into three groups, which, in order of age, are (1) the granites, 
(2) the olivine syenite with its related rocks, and (3) the rocks of the Cripple Creek 
volcano. 

GRANITE GROUP. 

Although there seems to be no very evident relationship between the several 
varieties of granite found in the district, Mathews has shown that when studied 
over a larger field, they present a marked-uniformity in mineralogical and chemical 
composition. An average analysis which he has published 0 illustrates the char¬ 
acter of this granitic type. 


a Jour. Geol., vol. 8, 1900, p. 237. 





102 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


Si0 2 ... 
A1 2 0 3 .. 
Fe 2 0 3 .. 
FeO... 
MgO.. 
CaO... 
Na 2 0.. 

k 2 o... 

H„0 - 
IL,0 + 


Average analysis of Cripple Creek granite. 


74.90 

Ti0 2 . 

12.89 

PA- 

.58 

F ... 

.91 

MnO 

.07 

BaO. 

.74 

Li 2 0. 

3. 10 


5.92 


.15 


.55 



Less O for F 


0 . 12 
.02 
.31 
Trace. 
Trace. 
Trace. 


100. 26 
.13 


100.13 


On comparison with analyses of typical granites of other localities,.he found 
that these Colorado granites are (1) rich in silica, (2) deficient in the sum of iron, 
magnesium, and calcium oxides, (3) normal in regard to the amount of total alkalies, 
but rich in potash and lienee correspondingly poor in soda, and (4) unusual because 
of their content of fluorine which is present as fluorite. To this the writer would 
add (5) that they are low in alumina. 


OLIVINE-SYENITE GROUP. 

The mineralogical evidence, as revealed by the microscope, makes it certain 
that an intimate genetic relationship exists between the pyroxene granite, pyroxene 
syenite with accessory olivine, olivine syenite, olivine gabbro and its doleritic 
contact facies, and the anorthosite dike of Iron Mountain, as well as nearly or quite 
all the diabase dikes of the district. Chemical investigations of these rocks have 
not been made, but it may be said that, in the order above given and excepting 
the anorthosite, they contain decreasing amounts of silica, alumina, and the alkalies, 
and increasing proportions of iron and lime. There is reason to believe that the 
content in magnesia reaches a limit in the olivine gabbro and is somewhat smaller 
in the contact facies of that rock and in the diabase. Even in the granite the 
amounts of silica, alumina, and alkalies are probably below the average for granite, 
while in the olivine gabbro and the diabase iron, magnesia, and lime are certainly 
high. Phosphoric acid is prominent in the olivine gabbro. The anorthosite, 
presumably the youngest rock of the group, probably contains rather low silica, 
high alumina and lime, and low soda. 

This group, which is younger than the granite group, is thus characterized on 
the whole by low silica and alumina, high iron, magnesia, and lime, and probabty 
a notable amount of alkalies. 

ROCKS OF THE CRIPPLE CREEK VOLCANO. 

For various reasons the rocks of the Cripple Creek volcanic group have been 
more thoroughly studied than those of the foregoing groups. Their distribution, 
being in general limited to the immediate vicinity of the volcanic center, has been 
conducive to obtaining a comprehensive and accurate idea of their mutual relations 
on the surface. The numerous mine workings, of which the majority are located 
in these volcanic rocks, add the great advantage of a third dimension to the geolog¬ 
ical relations seen on the surface and afford opportunity to collect fresh material 
which would not otherwise have been obtained. The interesting and compara¬ 
tively unusual character of the individual rock types has led to more or less careful 
investigation of each. 






















PETROLOGY-ROCKS OF THE CRIPPLE CREEK VOLCANO. 


103 


MINERALOGICAL CHARACTERS. 

As may have been inferred from a perusal of the description of these rocks, 
they have unquestionably been derived from some common source, or, as petrog- 
raphers say, from the same magma. The calculation of all the analyses into per¬ 
centages of constituent minerals would furnish a very valuable table for comparison 
of likenesses and differences throughout the series, but owing largely to the number 
of variable factors which would enter into such calculations it was found impracti¬ 
cable to do this. Since, with the exception of two varieties, the rocks are fine¬ 
grained porphyries it was likewise impossible to apply Rosiwal’s 0 metric method 
at all easily or accurately. But the more important minerals may be tabulated to 
show the mineralogical similarities and differences throughout this rock group. 
The characteristic and distinctive mineral of the phonolites is nehpeline; olivine 
may be said to occupy an analogous position in the basic rocks. The tegirine of 
the former is balanced by the augite of the latter. The abundant alkali feldspar 
of the one class has a prominence which is occupied by calcic plagioclase and by 
hornblende and biotite in the other. Xosean and sodalite are noticeable con¬ 
stituents of the phonolites; the basic rocks contain considerable quantities of 
apatite. Intervening members of the series are in general characterized by none 
or by smaller amounts of these distinctive minerals, or by a combination of minerals 
from both extremes. They also contain minerals of an intermediate composition, 
like the sodic plagioclases and aegirine-augite. So much for the mineralogical 
differences. The points of similarity are not so numerous, but are perhaps more 
striking. The most notable is the fact that orthoclase and analcite occur in 
practically all members of the series. Another point of likeness is that the extreme 
members are linked together through the intermediate character of the middle 
members just outlined. These features can perhaps be better presented in a table. 


Characteristic minerals in roclcs of Cripple Creek volcano. 


Phonolites. 

Intermediate rocks. 

Basic-dike rocks. 

Nepheline. 

Soda orthoclase. 

Albite. 


Algirine. 

JEgirine-augite. 


Sodalitel 

(Sodalite. 


Nosean J 

|Nosean. 



Orthoclase. 

Orthoclase. 


Analcite. 

Analcite. 


Apatite. 

Apatite. 


Augite. 

Augite. 


Oligoclase.. j 

(Labradorite. 


Biotite.i. 

| Biotite. 


HornblendeJ 

[Hornblende. 



Olivine. 


The conditions of cooling, as revealed by the texture of these rocks, apparently 
had but slight effect on the mineral composition. To be sure, the plutonic type, 
the syenite, often contains no analcite, but in other respects the mineral develop¬ 
ment is practically independent of texture. 


a Verh. Wien. geol. Reichsanst., 1898, vol. 32, pp. 143 fi. 





























104 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT 


CHEMICAL CHARACTERS. 


The foregoing relations, then, are almost wholly dependent on the chemical 
characters of the rocks, and are therefore expressed more exactly, although in a 
different light, in the following table of analyses. Tins is simply a compilation of 
the analyses appearing under each rock type, arranged approximately in the order 
of decreasing amounts of total alkalies, since these are the components which enter 
into orthoclase and analcite, the common minerals of the whole series, and which 
seem to constitute the most striking feature of the group. It is to be regretted 
that sufficient fresh material was not obtained for an analysis of the leucitophyre. 
It would probably correspond pretty closely with the phonolites, but would have 
an inverse ratio of potash to soda. 


Analyses of rocks from the Cripple Creek volcano. 



1. 

II. 

III. 

IV. 

V. 

VI. 

VII. 

VIII. 

IX. 

X. 

XI. 

XII. 

XIII. 

XIV. 

XV. 

XVI. 

SiC>2-... 

58.98 

58.78 

59.00 

58.64 

62.79 

59.38 

54. 43 

54.88 

54.34 

58.05 

56.01 

51.89 

49.84 

48.76 

47.31 

44.08 

AI2O3 — 

20.54 

20.03 

20.07 

19.62 

19.10 

19.47 

19.01 

18.53 

19.23 

17.66 

17.92 

17.94 

17. 78 

17.04 

16.21 

12.80 

Fe 2 C>3.. - 

1.65 

1.87 

1.58 

2.17 

2.29 

1.60 

2.85 

2.93 

3.19 

3.51 

4.20 

3.85 

5. 86 

5.04 

5.05 

4.58 

FeO.... 

.48 

.49 

.05 

.42 

.36 

1.19 

1.93 

1.92 

2.11 

1.65 

2.52 

3.37 

2.62 

3. 47 

2.90 

3. 72 

MgO.... 

.11 

.16 

.10 

.37 

.40 

.36 

.99 

1.26 

1.28 

1.55 

2.04 

2.88 

3.02 

4.57 

3.08 

7.22 

CaO.... 

.67 

83 

1.05 

1.24 

.87 

1.96 

4.33 

4.15 

4. 53 

4.48 

4.80 

5.62 

7.35 

8. 64 

7.11 

11.21 

Na 2 0...' 

9.95 

9.36 

8.34 

8.39 

6.23 

7.80 

6.92 

6.65 

6.38 

5.80 

4.92 

4.63 

5.20 

4. 27 

3.92 

2.97 

K 2 0.... 

5.31 

5.50 

5.63 

5.26 

5.58 

5.83 

5.07 

4.90 

5.14 

4.06 

4.21 

4.50 

3.04 

3.39 

3.73 

3. 31 

H 2 0- .. 

.19 

.31 

.24 

.34 

.25 

.11 

.31 

.38 

.14 

.35 

.31 

.72 

.34 

.69 

.87 

.77 

h 2 o+ . . 

.97 

1.57 

2.03 

2. 40 

.84 

.69 

1.68 

1.75 

1.17 

.87 

1.10 

2.09 

2.02 

1.84 

2.17 

2.35 

Ti0 2 .... 

.24 

.29 

.29 

.20 

.71 

.58 

.96 

.93 

1.09 

.91 

1.20 

1.34 

1.43 

1.34 

1.64 

1.43 

Zr0 2 .... 

.20 

.17 

.20 

.09 

.02 

.10 

.04 

.03 

.07 

.02 

.02 

.03 

.03 

Trace. 

.01 

None. 

C0 2 . 



.26 

.23 

Trace. 


. 14 

.13 




Trace. 

.52 

.22 

4.98 

4. 14 

P 2 Oo.... 

.04 

.03 

.05 

.03 

.12 

.08 

.25 

.27 

.27 

.40 

.55 

.67 

.76 

.79 

.90 

.70 

S0 3 . 

.20 

.12 

.07 

Trace. 

None. 

.37 

.42 

.36 

.07 

.04 

None. 

None. 

None. 

Trace. 

.05 

.01 

Cl. 

.28 

.58 

.24 

.14 

Trace. 

.22 

.22 

.14 

.28 

Trace. 

Trace. 

Trace. 

Trace. 

.01 

.05 

.04 






. 10 


.07 

. 10 



.04 

. 41 


. 11 

.12 

.26 

CroO't_ 














Trace? 

Trace? 

.05 

MnO.... 

.26 

.15 

.12 

.20 

.07 

.15 

.08 

.25 

.08 

.13 

.13 

.08 

.21 

.08 

Trace. 

.14 

BaO.... 

None. 

None. 

Trace. 

Trace. 

.14 

.13 

.21 

.18 

.24 

.19 

.16 

.19 

.22 

.15 

.17 

.13 

SrO. 

None. 

None. 

None. 

Trace. 

.03 

.03 

.21 

.11 

.16 

.08 

.06 

.11 

.18 

.07 

.02 

.06 

Li 2 0.... 

Trace. 

Trace. 

Trace. 

Trace. 

Trace. 

Trace. 

Trace. 

Trace. 

Trace. 



Trace. 

Trace. 

Trace. 

Trace. 

Trace 


100.07 

100. 24 

99.92 

99. 74 


100.05 

100.12 

99.85 

99.77 






100. 29 

99. 97 

Less 0 

















for Cl. 

.07 

. 14 

.06 

.03 


.05 

.05 

0.3 

.07 






.01 

.01 



















100.00 

100.10 

99.86 

99. 71 

99.90 

100.00 

100.07 

99.82 

99.70 

99.75 

100.19 

100.32 

100. 42 

100 48 

100.28 

99. 96 


I. Phonolite. 

II. Phonolite. 

III. Phonolite. 

IV. Phonolite. 

V. Biotite trachyte. 
VI. Latite-phonolite. 
VII. Latite-phonolite. 
VIII. Latite-phonolite. 


Miaskose.a 

Miaskose. 

Miaskose. 

Miaskose. 

Phlegrose.fc 

Miaskose. 

Essexose. 

Essexose. c 


Mitre Peak. 

Straub Mountain. 
Big Bull Mountain. 
Rhyolite Mountain. 
Portland mine. 

Buff Cliff. 

Bull Cliff. 

Portland mine. 


IX. Syenite. Akerose.d 

X. Latite-phonolite. Akerose. 

XI. Latite-phonolite. Akerose. 

XII. Syenite. Monzonose. 

XIII. Bull Cliff trachydolerite. Akerose. 

XIV. Isabella trachydolerite. Akerose.« 

XV. Vogesite. Monzonose. c 

XVI. Monchiquite. Ourose. 


Longfellow mine. 
Anaconda mine. 
Portland mine. 
Portland mine. 

Bull Cliff. 

Isabella mine. 
Jennie Sample mine. 
Block 8 mine. 


a According to the classification proposed by Cross, Iddings, Pirsson, and Washington, in “A Quantitative Classifica¬ 
tion of Igneous Rocks,” Chicago, 1903. 

i> On line between phlegrose and nordmarkose. 
c Near akerose. 
d Near essexose. 

«Near andose. 



























































PETROLOGY-ROCKS OF THE CRIPPLE CREEK VOLCANO. 


105 


K 


This table shows not only the close relation of each rock and each type of 
rock to those on either side of it, but it makes remarkably apparent a very gradual 
change from the Mitre Peak phonolite to the monchiquite. It expresses a con¬ 
siderable range in percentages of the essential oxides from one end of the series 
to the other as follows: 


Si0 2 .. 
At,0 3 . 
Fe 2 0 3 
FeO.. 
MgO. 


Range of 'percentages of essential oxides in roclcs of CApple Creek volcano. 


62.80-:'. 

00 

CaO. 

20. 50-12. 

80 

Xa.O 

5.60- 1. 

GO 

ivi>. 

3.80- 

40 

H.,0. 

7. 30- 

10 



11.20-0.70 
10.00-3.00 
5. 90-3. 00 
2.40- .70 


But in spite of these wide limits, the analyses show a close chemical relation¬ 
ship or consanguinity, not only in these principal constituents, but in the less 
usual or less abundant ones like titania, zirconia, sulphuric anhydride, and chlorine. 
The last two components particularly are characteristic of this rock group. The 
U noticeable percentage of combined water may be attributed mainly to analcite, 
but the fluid inclusions in apatite also account for an appreciable amount. 

Certain features are brought out more clearly when these analyses are converted 
into molecular proportions, as has been done below. The “serial character” 0 of 
this rock group is thus very well shown. 


Molecular ratios of essential oxides in rocks of Cripple Creek volcano. 



I. 

II. 

in. 

IV. 

V. 

VI. 

VII. 

VIII. 

IX. 

X. 

XI. 

XII. 

XIII. 

XIV. 

XV. 

XVI. 

SiC>2. 

0.983 

0.980 

0.983 

0.979 

1.046 

0.990 

0.907 

0.915 

0.906 

0.967 

0.933 

0. 865 

0.831 

0.813 

0. 788 

0.734 

AljOs. 

.201 

.196 

.197 

.192 

.187 

.191 

.186 

.181 

.188 

.174 

.175 

.175 

.174 

.167 

.159 

.126 

Fe2C>3 . 

.010 

.012 

.010 

.014 

.014 

.010 

.018 

.018 

.020 

.022 

.026 

.024 

.037 

.031 

.031 

.029 

FeO. 

.007 

.007 

.009 

.006 

.005 

.017 

.027 

.027 

.029 

.023 

.035 

.047 

.036 

.049 

.040 

.051 

M g o.: 

.003 

.004 

.003 

.009 

.010 

.009 

.025 

.031 

.032 

.039 

.051 

.072 

.075 

.114 

.077 

.180 

CaO. 

.012 

.015 

.019 

.022 

.016 

.035 

.077 

.074 

.080 

.080 

.086 

.100 

.131 

.154 

.127 

.200 

Na 2 0. 

.101 

.151 

.134 

.135 

. 100 

.126 

.111 

.107 

.103 

.094 

.079 

.074 

.084 

.069 

.063 

.048 

K 2 0 


.059 

.060 

. 056 

.060 

.062 

.054 

.052 

.054 

.044 

.045 

.048 

.032 

.036 

.039 

.035 

h 2 o+. 


.087 

.113 

.133 

.047 

.038 

.093 

.097 

.065 

.048 

.061 

.117 

.112 

.102 

.120 

.131 


From these figures certain other ratios may be obtained which also show the 
relations among the various rocks. Because of the definiteness and uniformity of 
composition of the phonolite group, the four phonolite analyses have been averaged 
and the resulting analysis designated by P. The other analyses are numbered 
according to the table on the facing page. 


Ratios of potash to soda in r.ocks of Cripple Creek volcano. 


1.. . 

11.. 

III. 

IV. . 
P... 

V. .. 

VI. . 

VII. 
VIII 


1 

: 2.87 

IX. 

. 1 

: 1.91 

1 

: 2.57 

X. 

. 1 

: 2.14 

1 

: 2.23 

XI . .. 

. 1 

: 1.76 

1 

: 2.41 

XII. 

. 1 

: 1.54 

1 

: 2.54 

XIII. 

. 1 

: 2.62 

1 

: 1.67 

XIV.'. 

. 1 

: 1.92 

1 

2.03 

XV. 

. 1 

: 1.61 

1 

2.06 

XVI. 

. 1 

: 1.37 

1 

2.06 





a Washington, H. S., The igneous complex of Magnet Cove, Arkansas: Bull. Geol. Soc. America, vol. 11, p. 403. 

I 









































































106 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

As in the case of some similar computations/ the middle members of this rock 
series show an approach to a constant ratio of potash to soda, the ratio in this case 
being about 1 : 2 , while the end members show greater variations, the ratio ranging, 
in round numbers, from 1 : 2.9 to 1 :1.4. This is a rather smaller range than has been 
found in many petrographic provinces . * * 6 These ratios also show a general increase 
in the prominence of potash from the phonolite to the monchiquite end of the series, 
though there are several exceptions to this rule. 

Without giving the figures for each rock, it may be stated that computation 
shows that the ratio of molecular proportions of total alkalies to the sum of Fe 2 0 3 , FeO 
MgO, and CaO ranges from 1:0.14 in the phonolites to 1 :5.54 in the monchi quite, 
with fairly even gradation between these limits. 

The ratio of molecular proportions of the sum of Fe,0 3 , FeO, MgO, and CaO to 
silica has a range of 1:33.8 in the phonolites to 1 : 1.6 in the monchiquite, illustrating 
the well-known tendency for these basic oxides to increase as silica falls. 

The following table brings out the fact that, beginning with the phonolites, the 
alumina and silica decrease less rapidly than the total alkalies, and that the change 9 
is fairly uniform. 


Ratios of total alkalies to alumina and silica in rocks of Cripple Creek volcano. 



K2O-F N&20. 

AI2O3. 

SiC>2. 


K2O-F Na20. 

A1203. 

SiOj. 

p. 

1 

0.98 

4.86 

XI. 

1 

1. 41 

7. 52 

V. 

1 

1.17 

6.54 

XII. 

1 

1.43 

7. 09 

VI. 

1 

1.02 

5.27 

XIII. 

1 

1.50 

7.16 

VII. 

1 

1.13 

5.50 

XIV. 

1 

1.59 


VIII. 

1 

1.14 

5. 77 

XV. 

1 

1.56 

7.72 

IX. 

1 

1.20 

5.77 

XVI. 

1 

1.51 

8.85 

X. 

1 

1.26 

7.01 



In the more alkalic rocks the close approach to unity of the ratio of alkalies 
to alumina is of interest when compared with the amount of minerals in those rocks 
which have this ratio—orthoclase, albite, nepheline, and analcite—together with 
the slight amount of alumina which enters into the pyroxenes in those rocks. In 
the phonolites soda orthoclase, nepheline, and analcite make up about 85 per cent 
of the rock. The excess of alkalies over alumina in this case is due to the soda in the 
segirine and to the excess of soda over alumina in sodalite and nosean. In the more 
basic end of the series the predominance of alumina over alkalies, when taken in 
connection with the comparatively small importance of the anorthite molecule, is of 
interest in showing that the alumina must enter largely into the composition of the 
pyroxene, forming augite instead of diallage or diopside, the minerals which would 
naturally be expected in such rocks. 


a Weed and Pirsson, Geology of the Castle Mountain mining district, Montana: Bull. U. S. Geol. Survey No. 139, 1896, 

pp. 137, 138. 

6 Weed and Pirsson, op. cit., p. 137. Washington, H. S., op. cit., p. 402. Iddings, J. P., The igneous rocks of Electric Peak 
and Sepulchre Mountain: Mon. U. S. Geol. Survey, vol. 32, 1899, p. 136. Adams, F. D., The Monteregian hills: Jour. Geol., 
vol. 11, 1903, pp. 265, 271. Pirsson, L. V., Igneous rocks of the Highwood Mountains, Montana: Bull. U. S. Geol. Survey No. 
237, 1905, pp. 172, 173. 





































PETROLOGY-ROCKS OF THE CRIPPLE CREEK VOLCANO. 107 

The above table shows a close relation between silica and alumina, which is 
better represented below: 


Ratios of alumina to silica in rocks of Cripple Creek volcano. 


P. 1 : 4.98 

V . 1 : 5.59 

VI .. 1 : 5. 18 

VII ... 1 : 4.82 

VIII .. 1 : 5.06 

IX . 1 : 4.82 

X . 1 : 5.56 


XI . 1 : 5.33 

XII . 1 : 4.94 

XIII . 1 : 4.78 

XIV . 1 :4.87 

XV . 1 : 4. 96 

XVI .a 1 : 5.83 


This agreement throughout the series is really very striking and constitutes one 
of the best proofs that genetic relations exist between all these rocks. It almost 
wholly excludes the possibility of there having been more than one original source, 
or, conversely, it furnishes very strong proof that these rocks were derived from a 
common magma. It shows, furthermore, that although considerable differentiation * 6 
has taken place, as indicated by the range of percentages on page 104, the silica and 
alumina have nevertheless clung together during the processes which caused this 
result—whatever lias affected the one has equally affected the other. 

This is the only instance known to the writer in which an almost absolute 
chemical consanguinity (the sole fundamental factor) has been shown to exist 
between the various rock types of a petrographic province. The nearest approach to 
proof of definite chemical relationship which has been found in the literature is the 
exposition of the serial relations of the various rocks in certain areas, as in the Little 
Belt Mountains in Montana 0 and in "the Magnet Cove laccolith in Arkansas.^ 

It is believed, moreover, that this practically constant ratio of alumina to silica, 
together with the intimate, gradually changing relationship of the other oxides 
throughout the series, constitutes the best evidence yet brought forward toward 
proving what has heretofore been only assumed e —that the common magma was 
originally homogeneous. 

From a mineralogical point of view, this alumina-silica ratio, which is approxi¬ 
mately 1:5, indicates a large proportion of molecules having the orthoclase-albite 
ratio, 1:6, combined with minerals like nepheline, analcite, the remaining plagio- 
clases, and the pyroxenes, which in general have a ratio of alumina to silica lower 
than 1:5. 

COMPOSITION OF THE ROCKS EXPRESSED BY DIAGRAMS. 

Certain of these relations between these rocks are very well shown when the 
proportions of the essential oxides are represented graphically. For this purpose 
the general method adopted by Iddings-f has been used, but a few modifications 
have been introduced. The individual diagrams, each representing one analysis, 
are constructed on four lines in the same plane, intersecting at a common point and 

a The exceptional divergence in this case may be partially due to the decomposition which the rock has undergone. 

6 The term differentiation is here used in the same limited sense as employed by Pirsson. See Eighteenth Ann. Rept. U. S. 
Geol. Survey, pt. 3,1898, p. 573; Twentieth Ann. Rept. U. S. Geol. Survey, pt. 3,1900, pp. 566-567; and Bull. U. S. Geol. Survey, 
No. 237, 1905, p. 183. 

e Pirsson, L. V., Twentieth Ann. Rept. U. S. Geol. Survey, pt. 3, 1900, p. 571. 

d Washington, H. S., Igneous complex of Magnet Cove, Arkansas: Bull. Geol. Soc. America, vol. 11,1900, p. 403. 

« Cf. Bull. U. S. Geol. Survey No. 139, 1896, p. 141. 

/ Prof. Paper U, S. Geol. Survey No. 18, 1903. • 


I 




















108 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

cutting the plane into sectors of 45° each. The accompanying chart (PI. X) shows 
the disposition of the oxides, the length of the radii representing the relative amount 
of the respective constituents. The silica can not be feasibly shown in these dia¬ 
grams because of its large amount. It seems desirable to separate the ferrous and 
ferric iron whenever possible, particularly in rocks of this kind where the asgirine 
molecule enters. It is a satisfaction to feel that such a separation is in this case per¬ 
fectly warranted by the accuracy of the analyses made by the chemists of the 
Survey. Water is essential in these rocks and has been given a place in the diagram, 
while titanic oxide has been omitted, both because of the difficulty in representing 
it and because of its comparatively small importance in the composition of this 
group of rocks. 

The center of each diagram is located with respect to a pair of coordinates, of 
which molecular proportions of silica are the abscissas and molecular proportions of 
total alkalies are the ordinates. This was the most practical manner of representing 
the silica, and as it is admittedly the most important constituent of igneous rocks it 
is perhaps not illogical to distinguish it from the other oxides. In the case of this 
particular rock series the total alkalies are of next importance and have been empha¬ 
sized by being made the other determinant of the position of the diagram. No 
particular advantage could be seen in Iddings’s method of using the ratio of total 
alkalies to silica as ordinates—at least for these rocks, where it seemed only to com¬ 
plicate and obscure the relations which it was desired to show. 

To continue a simile which Iddings has used, likening these diagrams to ships 
moving away from the observer, it may be said that a large spread of sail indicates 
high alkalies and alumina; a large hull indic-aft's high iron, magnesia, and lime; a 
high mast indicates much alumina; large draft points to high magnesia; upper 
sails out to starboard stand for soda and to port for potash; ferric iron is situated at 
the starboard rail and combined water at the port; ferrous iron and lime make up 
respectively the starboard and port sides of the hull; the farther to the right the 
diagram is situated on the chart, the more siliceous is the rock; the higher it is the 
more alkalic. The converse is of course true. 

Because of the definiteness and uniformity of composition of the phonolite 
group, the four phonolite analyses have been averaged® and the resulting analysis 
represented by the diagram P. The other diagrams are numbered according to the 
table on page 104. To these thirteen diagrams is added, in its proper position, the 
diagram representing the average rock of the earth’s crust (marked E) according to 
Clarke’s latest computation. 6 

The position which the Cripple Creek rocks occupy with reference to this average 
rock shows at once that they are in general low-silica, high-alkali rocks; that, with 
the exception of the biotite trachyte (No. V), which in several respects diverges from 
the series, the most siliceous rock corresponds to the average rock in silica content, 
and the least alkalic corresponds to it in the proportion of alkalies. 

A comparison of the individual diagrams with that of the average rock indicates 
also that on the whole the Cripple Creek rocks are alumina rich. Iron, magnesia, 
and lime are below the average in all but the last five members, in which they are 
above. Ferric iron is on the whole high, while ferrous iron is low. Magnesia 


a See p. 66 


b Bull. U. S. Geol. Survey No. 228, 1904, p. 19. 








PETROLOGY-ROCKS OF THE CRIPPLE CREEK VOLCANO. 


] 09 


exceeds the average only in two rocks; but lime is about equal to or greater than the 
average in most of the types. Water is on the whole a little high. 

The combination of high alkalies and alumina with moderate silica gives to this 
rock group the distinctive and rather uncommon feature of containing practically no 
quartz. 

AVERAGE ROCK OF TIIE CRIPPLE CREEK VOLCANO. 

Another and perhaps more valuable comparison might be made with the 
average rock of the earth’s crust if some quantitative relation could be instituted 
between the Cripple Creek rocks and the composition of the average rock of the 
volcano thus be obtained. 

By making certain assumptions, which are more or less supported by fact or 
probability, it is possible to obtain an approximate idea of the composition of the 
material extruded from the volcanic reservoir which must have underlain the 
Cripple Creek district. 

It has been shown in a preceding chapter (p. 21) that the main breccia area 
practically occupies the throat of the volcano and that the walls of this conduit 
are very steep. If all the masses of eruptive rock which appear at the surface 
continue with uniform size in depth, then their volumes would bear to each other 
the same proportion as their areas. But it is certain that the size of these masses 
does vary at different depths. Mine workings which extend as deep as 1,500 feet, 
however, do not indicate any noticeable change in the relative abundance of the 
various rock types, with the exception of two cases that will be considered presently. 

There is another fact also which tends to make a relation on the basis of area 
fairly representative. An uncertain but considerable amount of volcanic material 
has been removed by erosion. If, therefore, the contacts of a mass diverge down¬ 
ward, showing that the amount of material is greater below, they would in general 
have converged upward and have inclosed less of the rock than the present surface 
exposure indicates, and vice versa. Accordingly, while the surface area as now 
shown may not be an exact average cross section of the mass throughout its vertical 
extent, it nevertheless approaches such an average. 

Furthermore, only a glance at the map is needed to show that phonolite, latite- 
phonolite, and breccia comprise by far the greater proportion of the volcanic rocks. 
The breccia is made up almost wholly of the two other rocks, in approximately 
equal amounts. The composition of the latite-phonolite does not vary greatly 
from that of phonolite. Finally, the amount of phonolite occurring within the 
limits of the area mapped is only about half as great as the amount which occurs 
outside those limits, but in the same general locality, and which must of course be 
included in the computation. It is therefore possible to predict, without further 
estimates, that the average rock will have a composition between phonolite and 
latite-phonolite, and that it will be nearer to phonolite. It is obvious, therefore, 
that any inaccuracies which may enter into the calculation of the relative amounts 
of the different rocks, be they theoretical or mechanical, will be very much mini¬ 
mized by this fact. 

The two exceptions to the general rule that the igneous masses have on the 
average a nearly vertical contact are the Bull Cliff trachydolerite and some of the 
13001— No. 54—06-9 


110 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


bodies of latite-phonolite. The former certainly appears to decrease in amount 
with depth; but, as has been shown, its amount is so small relative to the total mass 
of eruptive rock that this error is practically insignificant. With the latite-phonolite 
the case is different. Large bodies are known to occur which are flat and ultimately 
give out in depth or diminish to comparatively narrow dikes; but, because of this 
flat shape, the actual horizontal extent of these bodies is in several known cases 
considerably greater than their area exposed on the surface. Moreover, flat bodies 
which do not appear at the surface have been encountered in some of the mine 
workings and this makes it fair to assume that still other buried masses of latite- 
phonolite exist at various depths. So, while the assumption that the present 
exposed area of this rock represents its relative volume is unfounded, still it does 
not seem at all improbable. But even if this assumption be wholly untrue the 
error which its use introduces is not so great as might at first appear. In all 
cases where the latite-phonolite has been found to give out in depth it has been 
underlain by breccia. But as has been shown, the breccia is composed of about 
half latite-phonolite; the other half, phonolite, is not very different in composition 
from latite-phonolite. Any error which may result from this assumption will 
therefore tend only to throw the computed composition of the average rock a little 
farther from phonolite than is actually the case. 

On the whole, therefore, the first of the following assumptions seems warranted, 
as well as the remaining ones: 

1. The volumetric proportion of the various rock types corresponds to their 
areal proportion on the present surface. 

2. The same specific gravity (about 2.55) may be assigned to all the rocks 
except the breccia, which is given 0.8 of that value. 

3. The breccia is composed of 5 per cent granite, gneiss, and schist; 50 per cent 
phonolite; and 45 per cent latite-phonolite. 

4. The narrow- phonolite dikes make up 1 per cent ot the total massive phonolite. 

5. The basic dikes have an average width of 4 feet, but because of their ready 
decomposition and consequent frequent escape of detection this width is increased 
to 6 feet. 

6. Of the basic dikes, the Isabella trachydolerite comprises 50 per cent, vogesite 
10 per cent, and monchiquite 40 per cent. 

The areas of the rocks were accordingly measured on the map by means of 
planimeter and scale, and are shovm in the table below: 


Areas of the Cripple Creek volcano rocks. 


Rock. 

Actual 
area.a 

Area cor¬ 
rected for 
breccia. 

Rock. 

Actual 
area.a 

Area cor¬ 
rected for 
breccia. 

Phonolite. 

Sq. miles. 
6.542 

Sq. miles. 

9.344 

Isabella trachydolerite 

Sq. miles. 
0.005 

.001 

.004 

6.636 

Sq. miles. 
0.005 

.001 

.004 

Biotite trachyte. 

. 130 

.130 

Vogesite. 

Latite-phonolite. 

.678 

3.039 

Monchiquite. 

Syenite. 

.143 

.143 

Breccia. 

Bull Cliff trachydolerite. 

.046 

.046 


12. 712 


a Of this, 4.230 square miles of phonolite and 0.169 square mile of breccia are not included by the Cripple Creek map. See 
Pikes Peak folio: Geologic Atlas United States, folio 7, U. S. Geol. Survey, 1894. 

























PETROLOGY-ROCKS OF THE CRIPPLE CREEK VOLCANO. 


Ill 


When these areas are computed into percentages the following result is obtained: 

Relative abundance of the Cripple Creek volcano rocks. 

Phonolite. 

Latite-phonolite. 

Biotite trachyte. 

Syenite. 

Bull Cliff trachydolerite 

This shows the surprisingly small importance of the basic rocks, and though the 
figure for the Bull Cliff rock may be somewhat too high, it makes very little differ¬ 
ence. The leucitophyre has, of course, been omitted, but the probably very small 
amount which was ever present would have little effect on the whole. 

In order to obtain from these figures the composition of the average rock of 
the volcano, it is necessary to make another assumption, viz, that the analysis of 
each rock type in cases where only one analysis has been made and the average 
of the several analyses where several have been made represent truly the average 
composition of the respective rock types. It may be said in the first place that 
material for analysis was chosen particularly to typify the group to which it belonged. 
In the case of those rocks of which only one analysis has been made, their relative 
amount is so small that the possible error arising from an unrepresentative analysis 
will have little effect on the total composition. In each case where several analyses 
have been made, it is believed that the average of these is fairly typical of that rock 
division. In the phonolites, which, as above shown, make up nearly three-fourths 
of the total, the five analyses are so nearly identical that in that case certainly the 
average analysis is a fair representation of the composition of the phonolites. 

By taking the above respective percentages of the average analyses of each 
rock type, an analysis is obtained which represents the average rock of the volcano. 

Composition of average rock of the Cripple Creek volcano. 


Per cent. 
73.505 
23.907 
1.023 
1. 125 
.362 


Per cent. 

Isabella trachydolerite. 0. 039 

Vogesite.008 

Monchiquite. .031 


100.000 


• 

I. 

II. 

III. 


I. 

II. 

III. 


58.23 

58.50 

0.975 

S0 3 . 

0.13 

0.13 



19.65 

19.75 

.193 

Cl. 

.26 

.26 


Fe 2 C >3 . 

2.16 

2.18 

.014 

FeS 2 . 

.01 



FeO 

.86 

.87 

.012 

Cr 2 Oj. 

Trace. 

Trace. 


MgO . 

. 47 

.47 

.012 

MnO. 

. 17 

.17 


CaO 

1.74 

1.76 

.031 

BaO. 

.05 

.05 



8.29 

8.34 

.134 

SrO. 

.02 

.02 


k 2 o 

5.27 

5.31 

.056 

Li 2 0. 

Trace. 

Trace. 


h 2 o 

.27 








1.61 

1.62 

.090 


99.99 

100.06 


Ti0 2 

. 43 

.43 


Less O for Cl. 

.06 

.06 



. 13 

. 13 






C0 2 

. 10 




99.93 

100.00 


P 2 Oo. 

.07 

.07 

. 






I. Average rock computed from analyses. 

II. Average rock with pyrite, carbon dioxide, and hygroscopic water excluded and recalculated to 100 per cent. 
III. Molecular proportions of II. 












































































112 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

By referring to the table on page 104, it is seen that, as was to be expected, this 
rock comes between the phonolites and latite-phonolites and agrees very closely 
with the most basic phonolite. 

A few words may be added concerning the meaning and value of this analysis. 
In arriving at this result the assumptions made have been perhaps wholly incapable 
of conclusive demonstration: they have been more or less arbitrary, and largely 
dependent on the personal factor. It is believed, however, that the result given is an 
approximation to the truth and hence of value. This average rock is not proposed 
as representing the “originally homogeneous magma” from which the various 
types of rock have been derived by segregation, differentiation, liquation, fractional 
crystallization, or other means. Some petrologists are led by principles of physical 
chemistry to believe that the material which is extruded from the main reservoir is 
often not representative of the total material in the reservoir. But it is believed 
that this analysis gives an approximate idea of the composition of the material 
which has issued from this volcanic reservoir; that is, the average rock of the 
Cripple Creek volcano. 

On comparing this analysis, which is represented on the chart (PI. X) as C, 
with that of the average rock of the earth’s crust, it is apparent that in silica con¬ 
tent the difference is not great, but it is very much richer in alkalies and contains 
noticeably more alumina. Ferrous iron, magnesia, and lime are very low in the 
Cripple Creek rock, but ferric iron and water are about the same as in the average 
rock of Clarke. 

The ratio of potash to soda in the average rock of the earth’s crust is 1: 1.75. 
The ratio of potash to soda in this average Cripple Creek rock is 1: 2.39, a figure 
considerably higher than the apparent mean value of 1: 2 in the table on page 105. 
It is believed that this illustrates the danger of placing too great confidence on 
deductions made from analyses without having regard to the quantitative relations 
of the rocks which the analyses represent. 

The ratio of total alkalies to the sum of Fe,0 3 , FeO, MgO. and CaO is 1:0.36. 
The ratio of this sum to silica is 1: 14.13. The predominance of ferric over ferrous 
iron accounts for the jegirine molecule in the phonolites. * 

The ratio of total alkalies to alumina and silica is 1:1.01 : 5.13, and of alumina 
to silica 1: 5.05. These last two ratios emphasize the nearly unit ratio of alkalies 
to alumina and confirm the statements made on page 107 as to the constant relation 
of alumina to silica in these rocks. 

The ratio of alkalies to alumina and silica is very nearly stoichiometric, but 
probably only by coincidence. 

The appearance of orthoclase and analcite as final separations from the molten 
material and the constant relation of alumina and silica throughout the series may 
be some indication of an approach to the eutectic composition for the original 
magma. 

Besides the essential oxides, high zirconia and chlorine and low phosphoric 
acid are characteristic of the Cripple Creek average when compared with the average 
rock of Clarke. 

If lavenite is present in the phonolites, the rock contains original fluorine. 


U S.GEOLOGICAL SURVEY PROFESSIONAL PAPER NO 54 PL. X 



JULIUS BIEN &CO.L1TM N V 















































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































' 





















































, 




















































































































































































































































































PETROLOGY-ROCKS OF THE CRIPPLE CREEK VOLCANO. 


113 


ORDER OF SUCCESSION OF THE ROCKS. 

It is impossible to believe that near the beginning of eruptive activity effusive 
types were not more abundant than the few occurrences mentioned would indicate. 41 
It is true, however, that by far the greater part of the rocks which now remain are 
intrusive. Latite-phonolite, together with syenite, was probably the first of these 
to be erupted. It was followed by phonolite, Bull Cliff trachydolerite, and the 
basic dike rocks in the order given. This sequence is a common one, beginning 
with a rock of intermediate composition, passing to one extreme, the phonolites, 
and thence finally to the other extreme, the basic dike rocks. These last do not 
appear to conform exactly to the general sequence, since the Isabella trachydolerite 
was probably erupted after the vogesite and monchiquite, but they are so similar 
in composition that they may best be considered as one group. In connection 
with the sequence, the radial grouping of the dikes is of interest. 

SUMMARY. 

The Tertiary volcanic rocks of the Cripple Creek district, except the rhyolite, 
afford an excellent illustration of a petrographic province, i. e., they have clearly 
been derived by differentiation from a single originally homogeneous magma. 
The average rock of the Cripple Creek volcano is characterized by very high soda, 
high potash, high alumina, noticeable sulphuric anhydride, chlorine, and zirconia, 
and low ferrous iron, magnesia, and lime. • All the rocks have approximately the 
same ratio of alumina to silica. 


a Cl. p. 20. 



CHAPTER IV.—GENERAL MINERALOGY OF THE DISTRICT. 


EIST OF MINERALS. 

For convenient reference, the names of the principal mineral species known 
to occur in the Cripple Creek district are assembled in the following list, which 
contains 68 established and 8 doubtful species: 


List of minerals of the Cripple Creek district. 


Gold. 

Rutile. 

Anorthite. 

Copper. 

Limonite. 

Sodalite. 

Tellurium? 

Psilomelane. 

Nosean. 

Petzite ? 

Molybdite. 

Nepheline. 

Sylvanite. 

Usemannite. 

Analcite. 

Krennerite. 

Calcite. 

Natrolite. 

Calaverite. 

Dolomite. 

Stilbite. 

Emmonsite. 

Rhodochrosite. 

Tourmaline. 

Tellurite. 

Barite. 

Olivine. 

Pyrite. 

Celestite. 

Augite. 

Marcasite ? 

Alunite. 

Diallage. 

Molybdenite. 

Gypsum. 

.ZEgirine. 

Stibnite. 

Glockerite ? 

Hornblende. 

Cinnabar? 

Chalcanthite. 

Arfvedsonite. 

Galena. 

Mirabilite. 

Biotite. 

Zinc blende. 

Mallardite. 

Muscovite. 

Chalcopyrite. 

Epsomite. 

Roscoelite. 

Tetrahedrite. 

Apatite. 

Chlorite. 

Chalcocite? 

Wavellite. 

Serpentine. 

Fluorite. 

Titanite. 

Kaolin. 

Quartz. 

Hubnerite. 

Chrysocolla. 

Chalcedony. 

Orthoclase. 

Morencite ? 

Opal. 

Microcline. 

Chloropal ? 

Magnetite. 

Albite. 

Coal. 

Specularite. 

Oligoclase. 


Zircon. 

Labradorite. 



NOTES ON OCCURRENCE. 

NATIVE ELEMENTS. 

Gold .—Within the oxidized zone of the veins native gold is abundant, but it 
rarely exhibits its normal characteristics. It forms small particles, many of which 
are entirely invisible to the naked eye, or in a few cases larger grains, spongy masses, 
thin sheets, or plates. Occasionally elongated forms with grooved surfaces are 
found which more or less plainly show their character as pseudomorphs after calave- 
rite or other tellurides. The color is dull brownish, not unlike that of limonite, 
but the true tint and luster is quickly shown upon slight pressure with a knife. 


114 


I 


\ 


MINERALOGY-THE TELLURIDES. 115 

Its texture is spongy and brittle. In places it is covered by rusty fdms of a ferrugi¬ 
nous compound containing tellurium (Penrose), and this coating often interferes 
with amalgamation. The gold of Cripple Creek is of great purity; sometimes, 
indeed, silver is present only in traces. 

Free gold does not, as a rule, occur in the veins except where set free by oxidation. 
To this general statement there are, however, some exceptions. Bright gold of 
normal characteristics occurred on a seam with roscoelite in the El Paso mine and 
in tetrahedrite in the lower levels of the Doctor-Jackpot mine. Similar gold is 
reported to have occurred in the Laura Lee mine, on Mineral Hill. Examination 
of some telluride ores, supposedly free from oxidation, seems to indicate that a 
very small part of the gold is free; it is, however, very difficult to assert that no 
oxidation has taken place. The beginning of this process is indicated by a thin 
brown film on the telluride crystals. 

The placer gold, chiefly won from the southwest slopes of Mineral Hill, has 
the same characteristics as that from the oxidized zone of the veins. 

Pseudomorphs of this rusty and spongy gold after calaverite and other tel- 
lurides are common. They usually show the normal prismatic form of the calave¬ 
rite and their faces are often warped and shrunken by loss of volume. Fine speci¬ 
mens of these pseudomorphs were seen from the Mercer and Zenobia veins. In 
the latter case their surface was covered by a film of opal. 

Silver .—No native silver is reported from the district, although it might well 
form in places by the oxidation of tetrahedrite, some of which is very rich in this 
metal. Penrose reports a locality “on the hill above the Rosebud mill”® near the 
confluence of Cripple Creek and Arequa Gulch, where the gold contains 40 per cent 
of silver. 

Copper .—Native copper was noted in a specimen from an altered basalt dike 
on the Hillside claim on Tenderfoot Hill. A seam containing partly crystallized 
copper is reported to have been found on Mineral Hill. The mineral might easily 
form by the oxidation of tetrahedrite. 

Tellurium .—Tellurium has been reported from Raven Hill in crystallized form, 
but the find is not authenticated. Its general absence from the veins of the district 
is somewhat remarkable. 

THE TELLURIDES. 

As th£ principal ore minerals of Cripple Creek consist of tellurides, a brief review 
of the various compounds known in nature and belonging to this class may be of 
interest. The principal telluride of Cripple Creek is calaverite, although occurrences 
of sylvanite and petzite are also common. 

The tellurides are minerals with metallic luster, usually soft, the hardness rarely 
exceeding 3; semisectile or brittle. The specific gravity is usually about 9; calave¬ 
rite is the heaviest of the number and reaches 9.4. 

Coloradoite .—Mercuric telluride (HgTe). Massive; iron black; not definitely 
known from Cripple Creek. 

a Penrose, R. A. F., jr., Mining geology of the Cripple Creek district: Sixteenth Ann. Rept. U. S. Geol. Survey, pt. 2, 1895, 

p. 120. 





116 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

11 Kalgoorlite." —Supposed telluride of gold, silver, and mercury (HgAu 2 Ag 6 Te 6 ). 
Probably a mixture of petzite and coloradoite. a Iron black; not known from 
Cripple Creek. 

Melonite. —Nickel telluride (Ni 2 Te 3 ). Reddish white; granular or foliated; not 
known from Cripple Creek. 

Altaite. —Lead telluride (PbTe). Tin white, with yellowish tinge ; massive, with 
cubic cleavage; not known from Cripple Creek. 

Hessite. —Silver telluride (Ag 2 Te; Te 36.7, Ag 63.3). Sometimes with up to 13 
per cent gold. Isometric; lead gray or steel gray; not known from Cripple Creek. 

Petzite. —Telluride of silver and gold (Ag,Au),Te. Ag:Au = 3:l. Te 32.5, 
Ag 42, Au 25.5. Massive; steel gray to iron black; stated by T. A. Rickard to occur 
on the Geneva claim of the Gold King mine. 

Tetradymite. —Sulphotelluride of bismuth (Bi,(Te,S) 3 ). Steel gray; massive or 
small crystals. This is the most wide-spread tellurium mineral, but it is not known 
from Cripple Creek. 

Nagyagite. —A sulphotelluride of gold and lead, with varying composition. 
Gold 6 to 13 per cent. Tabular crystals; blackish or lead gray; not known from 
Cripple Creek. 

The tellurides which enter into the ores of Cripple Creek have the general formula 
(Ag,Au)Te 2 and comprise the three species calaverite, sylvanite, and krennerite. 

Sylvanite. —Telluride of gold and silver [(Au,Ag)Te,]. Au :Ag=l:l. Te 62.1, 
Ag 13.4, Au 24.5. Monoclinic; usually crystallized or in arborescent forms; twins 
frequent, specific gravity = 7.9 —8.3; excellent cleavage; color pure steel gray or 
silver white, inclining to yellow. The name of sylvanite is derived from the province 
of Transylvania, Hungary, where it was first found. The presence of this mineral in 
Cripple Creek was first suggested by Mr. R. Pearce 6 on the basis of an analysis of ore 
from the Moose mine; but the mineral was finely divided and some silver ore like 
tetrahedrite might easily have been present. Since then the presence of typical 
crystallized sylvanite has been shown by Dr. Charles Palaehe/ the occurrences being 
at the Mabel M. and Little May mines, and from another doubtful locality, the 
material being obtained from Mr. F. M. Woods, of Victor. The small crystals are 
thin-tabular parallel to b (010) and are bordered by planes of the orthodome zone. 
T. A. Rickard d states that the mineral has been found at the Independence, Port¬ 
land, Moon-Anchor, and Anchoria-Leland mines. During our investigation it was 
also identified from the Elkton and Blue Bird mines. 

Krennerite. —Telluride of gold and silver [(Au,Ag) Te,]. Composition variable. 
The original analysis of material from Xagyag, Transylvania, gave 19.44 per cent of 
silver. The analysis of Cripple Creek material gives Au 43.86, Ag 0.46, Te 55.68, or 
practically the same composition as calaverite. Orthorhombic; crystals normally 
developed; prismatic with striated prism combined with pinacoid and domes. 
Identified from the Independence mine/ 

“ Spencer, L. J., Mineralogical notes on Western Australian tellurides; the nonexistence of “kalgoorlite” and “coolgardite 
as mineral species: Min. Mag., vol. 13, 1901-1903, pp. 268-290. 
b Proc. Colorado Sci. Soc., vol. 5, 1894-1896, p. 15. 

cZeitschr. 1. Krystall. u. Min., vol. 34, 1901, p. 539. Also Am. Jour. Sci., 4th ser., vol. 10, 1900, pp. 419-422. 
d The Cripple Creek gold field: Inst. Min. and Met., London, vol. 8, 1899. 
f Myers, W. S., and Penfield, S. L., Am. Jour. Sci., 4th ser., vol. 5, 1898, p. 376. 






MINERALOGY-THE TELLURIDES. 


117 


Calaverite .—Telluride of gold and silver [(Au,Ag) Te,]. This mineral, previ¬ 
ously known from Boulder County, Colo., and from Calaveras County, Cal., was first 
identified from Cripple Creek by F. C. Knight “ in 1894. About the same time it was 
found at three separate localities in the district by Doctor Hillebrand. 6 Elaborate 
studies of its crystallography were made in 1901 and 1902 by S. L. Penfield and 
W. E. Ford c in the United States and by G. F. Herbert Smith and G. T. Prior/ in 
England. 

Some of the calaverite from Cripple Creek differs from that of other localities in 
having an exceptionally small percentage of silver. Most of the following analyses 
were made of well-crystallized material. 


Analyses of calaverite from Cripple Creek. 



i. 

2. 

3. 

4. 

5.o 

6 .b 

7. 

8. 

Te. 

56.22 

57.60 

57.40 

57.30 

(57. 25) 
40.99 

(56. 75) 
42. 77 

57.87 

56.93 

Au. 

40.14 

39.17 

40.. 83 

41.80 

41.66 

41.90 

Ag. 

3.63 

3.23 

1.77 

.90 

1.74 

.40 

.77 

.79 



99.99 

100 

100 

100 

99.98 

99.92 

100.30 

99.62 


a Plus gangue 0.02 per cent; tellurium by difference. b Plus gangue 0.08 per cent; tellurium by difference. 

1. F. C. Knight, Cripple Creek. 

2. W. F. Hillebrand, Prince Albert mine.) 

3. W. F. Hillebrand, Raven mine. >Specific gravity, 9.0, impurities subtracted. 

4. W. F. Hillebrand, C. O. D. mine. 

5. Penfield and Ford, Monument mine. Specific gravity, 9.328. 

6. Penfield and Ford, Cripple Creek. Specific gravity, 9.388. 

7. Smith and Prior, Raven Hill. Specific gravity, 9.155. 

8. Smith and Prior, Cripple Creek. Monoclinic. 

The calaverite occurs commonly in slender, deeply striated prisms, elongated 
in axis of symmetry. Ordinarily they are very small, but sometimes reach 1.5 
cm. in length. The faces have very high indices and do not fall in zones. On the 
whole the development is extremely unusual and presents some features difficult to 
explain. The axial ratio and angles resemble those of sylvanite. Smith and Prior d 
attempt to account for this puzzling crystallographical development by assuming 
triclinic symmetry accompanied by complicated twinning—of which, however, 
there is little external evidence—and believe that the crystals consist of an “inter¬ 
mingling of different structures, indicating that the crystals are really not homo¬ 
geneous. ” Massive calaverite occurs more rarely, but was noted from the Blue 
Bird mine; it has here a more bronzy-yellow color. There is no cleavage, a notable 
distinction from sylvanite. Brittle; hardness, 2.5; color, silver white, with a yel¬ 
lowish tinge. The calaverite from the original localities, as well as that from Kal- 
goorlie, Western Australia, has a pale, bronze-yellow color, usually absent in the 
Cripple Creek mineral, which in small particles is rather difficult to distinguish 
from pyrite. Calaverite occurs massive only in certain granitic and phonolitic 

a Proe. Colorado Sci. Soc., vol. 5, 1894-1896, pp. 66-71. 

* Geology and mining industries of Cripple Creek district: Sixteenth Ann. Rept. U. S. Geol. Survey, pt. 2,1895, pp. 133-135. 

« Am. Jour. Sci., 4th ser., vol. 12, 1901, pp. 225-246. 

d Min. Mag., vol. 13, 1902, pp. 122-150. 

























118 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

replacement ores. It is usually in the form of ill-defined crystals on quartz crusts, 
more rarely on fluorite or dolomite crusts. Fine crystals were obtained from the 
Conundrum mine, where they occur in vugs with fluorite in gneiss. Silver-white, 
thin, and bladed crystals, often showing radial arrangement, were found on joint 
cracks in the breccia of the Captain stopes of the Portland mine. Sometimes the 
crystals are contained in crystalline comb quartz (El Paso, C. Iv. & N., and Gold 
Dollar mines), or in chalcedony (Last Dollar mine). 

OXIDIZED TELLURIUM COMPOUNDS. 

The presence of oxidized compounds containing tellurium was first proved 
by Dr. R. Pearce. a In the same year F. C. Knight analyzed a light-brown, brittle 
substance, with bright-yellow streak occurring mixed with a metallic telluride, and 
found that, subtracting the telluride, it gave the composition under I and II. 


Analysis of tellurium compound from Cripple Creek. 


* 

I. 

II. 

III. 


30.27 

35. 44 

32.72 

Te0 2 . 

68.05 

62.79 

65. 45 

H 2 0. 

1.68 

1.77 

1.83 



100.00 

100.00 

100.00 


This would correspond to a ratio Fe 2 0 3 : TeO, : 11,0 = 2 : 4 :1 and to the formula 
2(Fe,0 3 , 2Te0 2 ) + H,0, requiring the composition given under III. No name was 
given to this compound, the homogeneity of which is, indeed, somewhat doubtful. 

Mr. Knight reports the presence of about a third of 1 per cent of selenium, 
but this element has not been discovered in any subsequent analyses of Cripple 
Creek ores. 

Two other tellurites have been described. The first is emmonsite, discovered 
by Hillebrand in a specimen from near Tombstone, Ariz., and also essentially a 
hydrated ferric tellurite. The second is durdenite, found by Dana and Wells in 
specimens from Honduras. This is a greenish-yellow, massive substance containing 
TeO, 67.1, Fe 2 0 3 27.7, H,0 10.2. Ferrotellurite and magnolite (Genth) from Boul¬ 
der County, Colo., have, probably, the compositions FeTe0 4 and Hg,Te0 4 , but 
neither species is satisfactorily established. 

Emmonsite .—A small quantity of a yellowish green tellurite was collected at 
the W. P. H. mine, Cripple Creek, where it occurred in a very rich pocket of ore, 
together with native gold and partly oxidized calaverite. The vein cuts granite 
and schist near the contact with volcanic breccia, and the pocket occurred at a 
depth of 245 feet. A similar substance occurred with rusty gold in the Moose mine 
and is reported from the Deadwood mine. It is probably general^ present in the 
rich, partly oxidized ore, though it has usually escaped detection. Dr. W. F. Hille¬ 
brand has examined this substance carefully, with the results in the quotation 
below. 6 

a Proc. Colorado Sci. Soc., vol. 5, 1894-1896, pp. 66-71. 

b Hillebrand, W. F., Emmonsite (?) from a new locality: Am. Jour. Sci., 4th ser., vol. 18, December, 1904, pp. 433-434. 














MINERALOGY-OXIDIZED TELLURIUM COMPOUNDS. 


119 


The mineral occurs as irregular small masses of yellowish green color, which 
often assume mammillary forms, the largest observed being about the size of a pea. 
Doctor Hillebrand says: 

In its optical properties, so far as they were determinable, there is no positive disagreement with those 
reported for emmonsite. Mr. W. T. Schaller reports as follows: 

“There are two cleavages, one parallel to b (010) and another parallel to a form in the orthozone. Axial 
plane parallel to b (010). Bx a perpendicular to a cleavage face in the orthozone. The extinction on the clino- 
pinacoid is inclined 25° to 30° to the vertical axis. 2E is approximately 40°. Double refraction medium, 
and the mineral is nonpleochroic.” 

****** * 

Like emmonsite, the mineral melts at a low heat to a red-brown liquid, but, unlike it, gives on stronger 
heating only tellurous oxide, with no trace of selenium or selenious oxide. Analysis confirmed the absence of 
selenium. Its density, too, differs from that of emmonsite, if the determinations in both cases on scanty 
material are to be depended on. After allowance for gangue the original emmonsite was judged to have a 
density of at least 5, while that of the present mineral is but little above 4.53, after allowing for 24.44 per 
cent of gangue, consisting mainly of quartz and to which the specific gravity of quartz was assigned. 

In its appearance the present mineral would seem to resemble durdenite more than emmonsite, but the 
marked difference in water content differentiates it sharply from that mineral, durdenite yielding over 10 per 
cent. 

After deducting 22.44 per cent of gangue, containing over 90 per cent of silica, three portions of from 
0.15 to 0.20 gram net weight each gave the following results: 


Analysis of emmonsite (?) from Cripple Creelc. 



i. 

2. 

3. 

Mean. 

Ratios. 

TeOs . 

70.83 

71.80 

70.20 

70.71 

3.16 


22.67 

22.81 

22.79 

22.76 

1.00 

HjO . 



( -21 

.21 



1 4.68 

4.82 




HjO+ . 

j 


. 

4. 54 

1.77 

Pj0 5 . 

.34 



.34 


AI.Oj . 


.58 

.54 



RiO*. p.t.p. o .... 




.88 





100.00 



a Includes alkalies, traces of MgO and of gold, and a small amount of a metal or metals precipitable by hydrogen sulphide, 
whose identity could not be established. 


Allowing the alumina to offset the P 2 0 5 , though it may belong to a soluble silicate or to the tellurite and 
a small portion of iron be demanded for the P 2 0 5 , the ratios given in the final column result. They are as 
unsatisfactory as those afforded by the original emmonsite, which were for Fe 2 0 3 : Te0 2 , 1 : 3.65 in the original 
description and 1 : 3.75 : 1.82 for Fe 2 0 3 : Te0 2 : H 2 0 if the supplementary determinations in this journal, 
xl, 81,1899 are accepted. The presence of tellurite in association with the green mineral suggests a possible 
explanation of the failure to obtain a simple ratio, though such contamination was not noted in the material 
analyzed nor on the neighboring gangue. If this explanation is correct, however, the variation from the orig¬ 
inal emmonsite ratio becomes still more marked. Provisionally the mineral may be regarded as emmonsite. 

The above results are given in some detail, notwithstanding their inconclusiveness, because of the impor¬ 
tance of accumulating data regarding the as yet small but interesting group of ferric tellurites and of inciting 
collectors and mining men to careful search for and preservation of material for more extended study. 

Thus far emmonsite, durdenite, and an unnamed mineral from Cripple Creek, described by Knight in 
the Proc. Colorado Sci. Soc., v, 66, and affording likewise unsatisfactory ratios, comprise the list of natural 
ferric tellurites, the formula of no one of which can-be regarded as established beyond question. 

























120 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

Tellurite .—The pure tellurium dioxide, Te0 2 , forms slender orthorhombic 
prismatic crystals and small spherical masses. It is a soft white or yellowish-white 
mineral of adamantine luster, with excellent cleavage. It has been identified by 
Doctor Hillebrand from the W. P. H. mine at Cripple Creek and occurs also at the 
Gold Sovereign and Blue Bird mines. It is confined to the oxidized zone. 

SULPHIDES AND SULPHANTIMONITES. 

Pyrite .—This mineral is the most common sulphide in the district. It occurs 
disseminated in the altered breccia and other volcanic rocks, but is most abundant 
in or near the veins. Disseminated in the rocks, it is usually crystallized, showing 
pyritohedral forms; the small crystals coating quartz crusts in the veins show the 
same form, occasionally also simple octahedrons or combination of cube and octa¬ 
hedron. At the Galena and C. K. & N. mines it forms thin reniform coatings on quartz 
and has a radial fibrous structure. It commonly occurs in massive form, in veinlets, 
or occasionally in large, irregular masses. It was thus observed in the granite ores 
of the Portland, Ajax, and Elkton mines, in the cross veins of the Last Dollar mine, 
and near Vindicator shaft No. 2 on level 3, near the Hull City line. Well-formed 
crystals one-half inch in diameter occur in the Lost Anna vein. The pyrite is usu¬ 
ally very poor in gold, but sometimes cupriferous, as shown by copper stains on 
the 1,000-foot level of the Portland mine. Two pure crystallized specimens exam¬ 
ined by Hillebrand proved to be without even a trace of gold. a At the localities 
just given the pyrite is also nearly barren. It is believed that in most cases the gold 
contents of the pyritic ores of Cripple Creek are due to admixed tellurides. 

Marcasite .—Crystal growths doubtfully referred to marcasite occur in Strat¬ 
ton’s Independence mine on crusts of dolomitic carbonates. 

Molybdenite .—The molybdenum disulphide frequently appears in the ores as 
oft lead-gray scales, particles, and smaller masses, more rarely covering slickensides, 
and is on the whole very inconspicuous. As seen under the microscope it forms 
flocculent aggregates, and is very commonly intergrown with pyrite and zinc 
blende. It has generally been overlooked, but without doubt is a very character¬ 
istic part of the vein matter. It occurs at all depths below the oxidized zone and 
has been identified from the Vindicator, Findley, Last Dollar, Mary McKinney, 
Moose, Portland, and several other mines. 

The mixed ores analyzed at the chlorination mills of the United States Reduc¬ 
tion and Refining Company at Colorado City contain about 0.04 per cent 
molybdenum. 

A little molybdenite was also found in a quartz veinlet 1 mile southwest of 
Cripple Creek, in gneiss. This veinlet is probably older than the gold veins of 
Cripple Creek. 

Stibnite .—The sulphide of antimony is of common occurrence in the Cripple 
Creek district in association with rich gold ores. In the usual groups and bunches 
of brilliant, steel-gray, striated prismatic crystals it is found in the C. K. & N. and 
El Paso veins, in the former in masses weighing up to 50 pounds. Other occurrences 
are in the Mary McKinney, Puzzle, Katinka,*Blue Bird, and Stratton’s Independence 

“Penrose, R. A. F., jr., Mining geology of the Cripple Creek district: Sixteenth Ann. Rept. U. S. Geol. Survey, pt. 2 
1895, p. 122. 







MINERALOGY-SULPHIDES AND SULPHANTIMON1TES. 


121 


mines, and it is probably entirely absent from few of the prominent veins of the 
district. The stibnite is frequently rich in gold, but this seems to be due to an 
admixture of calaverite, as was chemically proved in the case of rich stibnite from 
the C. K. & N. mine. 

Cinnabar (with native mercury).—According to Mr. Brown, an assayer at 
Cripple Creek, a little cinnabar, with some native mercury, was found in the Moon- 
Anchor vein. This is the only reported occurrence of this mineral in the district. 
The mineral was identified in the specimen. 

Galena .—In very small quantities this mineral is probably almost universally 
distributed in the ores. It is not always, however, perceptible to the naked eye. It 
has been observed with telluride ore in the Emerson and Bobtail veins of Stratton’s 
Independence mine, in the Buena Vista vein of the Isabella mine, in the Vindicator 
vein, in the Gold Coin, Dillon, Theresa, Blue Bird, Portland, Lost Anna, Anna Lee, 
Last Dollar, and Blue Bell veins; also in the rich pocket of the W. P. II. vein. 
Apparently it is rather more abundant in the western part of the district and occurs 
here in places in considerable quantity in small veins, some of which are not notably 
auriferous. Other occurrences are near the Fluorine mine on Copper Mountain, 
at several places along Spring Creek, at the Deerhorn, Ironclad, and Abe Lincoln 
mines (here coarsely crystalline), Chicago and Cripple Creek tunnel, Puzzle, Pointer, 
Midget, Conundrum, Moon-Anchor, Moose, C. K. & N., and El Paso mines. The 
mineral occurs at all depths, but within the oxidized zone is partly altered to cerus- 
site and anglesite (Penrose). The galena, while containing some silver, is not often 
strongly auriferous. 

Zinc blende {sphalerite ).—Next to pyrite, zinc blende is the most common 
metallic mineral accompanying the gold tellurides. It is probably present in every 
important vein. The mineral is usually of a reddish-brown color and occurs as 
small masses intergrown with pyrite, galena, and fluorite. It is not known to form 
distinct crystals. In fairly large quantities it was observed in the ores of the Blue 
Bell and Puzzle veins, associated with galena and covered by quartz and telluride; 
also in the Bonanza King vein of the Midget, in the Pointer, and in the lead vein of 
the Moon-Anchor. The Portland ore contains about 1 per cent of zinc blende. 
The mineral occurs at all depths, but in the oxidized zone it is usually converted 
to soluble sulphate. The dark-brown zinc blende from the Last Dollar mine con¬ 
tains, according to Hillebrand, a considerable amount of cadmium. 

Chalcopyrite .—This mineral, elsewhere so common, occurs very rarely in the 
district. It has been noted as a thin coating on tetrahedrite from Blue Bird mine. 
The few oxidized copper ores seem to be derived from tetrahedrite. 

Tetrahedrite .—This mineral, a sulphantimonite of copper, usually referred to as 
“gray copper,” is practically the only primary copper ore of the district. It gen¬ 
erally occurs in dark steel-gray masses with a reddish-brown streak, sometimes so 
red as to suggest specular iron ore. It is occasionally crystallized in tetrahedrons 
(Abe Lincoln and Doctor-Jackpot mines). It always contains silver, sometimes in 
large amounts, and most of the ore rich in silver which is shipped from the district 
carries a considerable amount of tetrahedrite. It occurs in the veins throughout 
the district and at all levels. The statement has sometimes been made that this 
mineral begins to be more abundant at a certain depth supposed to mark the 


I 


122 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


beginning of a zone of secondary sulphide enrichment, but this is erroneous. Occur¬ 
rences noted are as follows: 

Yellow Bird claim (Ellen McGregor group), near surface. 

Vindicator mine, 1,200-foot level. 

C. O. D. mine, level 10. 

Wilson claim, Bull Hill, surface. 

Prospect, 2,000 feet north of Iloosier mine. 

Ironclad mine, level 6. 

Puzzle vein, 60 feet above Ophelia tunnel. 

Isabella mine, Buena Vista vein, many levels, especially level 4. 

Isabella mine, Empire No. 2 vein, level 11. 

Isabella mine, Cheyenne vein, level 11. 

Mountain Monarch mine (near Doctor-Jackpot), level 2. 

Trachyte mine, 110-foot level (with 800 ounces silver per ton). 

Pointer mine, probably in all levels. 

Accident mine, probably in all levels. 

Anaconda mine, adit level. 

Last Dollar mine, levels 5, 10, and 12. 

Blue Bird mine, on 1,350-foot level; oxidized zone above was rich in silver. 

Dolly Varden mine. 

Sunset-Eclipse mine, 50 feet below surface. 

Hull City mine, in Shaft vein for 300 feet between levels 8 and 11. 

Doctor-Jackpot mine, 550 to 700 feet, Morning Glory levels. 

Moose mine, level 15. 

El Paso mine, level 1 (old workings). 

Portland mine, Lost Anna vein, level 10. 

CTialcocite (?).—A sulphide of copper, probably chalcocite, has been found in 
the Uncle Sam mine. 

Arsenopyrite .—We have not observed this mineral, which certainly is rare in 
the district. Mr. Edward W. Brooks, formerly chemist of the Ajax mine, states 
that it occurs occasionally with finely divided pyrite. 

OXIDES, CARBONATES, SULPHATES, SILICATES, ETC. 

Fluorite .—As a primary constituent of granite, fluorite occurs on Pikes Peak 
and probably also in the small area of Spring Creek granite in the northwestern 
part of the Cripple Creek district. It lias not been found in any other granites or 
fresh igneous rocks within the district. As a vein-forming mineral fluorite is very 
abundant, occurring in smaller or greater quantities in almost ever} 7- vein. It is 
ordinarily of a purple color of varying intensity, often very dark and rarely pale or 
colorless. The tendency toward crystallization is very marked, though the crystals 
rarely exceed 5 mm. in diameter. The universal form is the cube, in which form 
the mineral, together with quartz and dolomite, often coats the vugs and crevices 
in the rocks. Even when forming a solid vein filling the apparently granular mass 
consists of minute cubes cemented by quartz. To a limited extent the fluorite 
also appears as a product of replacement in all the various rocks in which the veins 
occur, especially in the so-called “granite ore.” 

Just outside the boundaries of the area represented on the map on both sides 
of Cripple Creek Canyon, purple and light-green fluorite occurs in narrow veins in 
granite. Whether these belong to the same period of vein-forming activity as the 
principal veins is doubtful. 


ft 


GENERAL MINERALOGY OF THE DISTRICT. 123 

Quartz. —Quartz is an important constituent of the older rocks, including 
granites, schists, and gneisses, but is generally absent from the younger volcanic 
rocks. It is one of the principal vein minerals occurring in every mine, chiefly 
forming crusts and combs, granular masses, or mammillary forms in the little fissures, 
and, to a minor degree, replacing the constituents of the adjoining rock. It has 
the usual forms of prism and pyramid, but the crystals are commonly small. Many 
of them appear rounded as if corroded. It is frequently intergrown with calaverite. 
In some places a late silicification has taken place, the quartz replacing earlier vein 
minerals, in part celestite. Smoky quartz with distinct dicliroism of carmine 
brown and pure brown occurs on crusts in the Ironclad mine. 

Chalcedony. —This mineral occurs sparingly as a filling between quartz crystals 
and is rather common as an incrustation lining small vugs in the veins. 

Opal .—The hydrated amorphous silica is not uncommon in Cripple Creek, but 
generally represents the last phases of vein-forming action, and forms also during the 
process of oxidation. It is especially abundant in the Zenobia mine as yellow 
masses, often like tangled wires or rods. It is sometimes found in vugs at consid¬ 
erable depth, as on the 1,000-foot level of the Gold Coin vein. Hyalite, a colorless 
opal, occurs in cracks of the Anaconda dike.® In the Victor and Buena Vista veins 
is found a brilliant-red siliceous mineral consisting essentially of 72 per cent silica, 
18 per cent ferric oxide, 1 per cent potash, and 3 per cent water." 

Magnetite (with ilmenite and titanomagnetite).—These are minor constituents 
of schist, diabase, latite-phonolite, basalt, and other rocks. Magnetite also occurs 
in a pegmatite dike in the town of Cripple Creek. 

Specularite. —This has been observed only once as a vein-forming mineral 
inclosed in quartz. It has also been reported to occur in a pegmatite dike on Rhyo¬ 
lite Mountain. In the form of hematite it is probably present in a finely divided 
state in the oxidized rocks. 

Zircon. —Occurs in microscopic form as an accessory constituent in most of 
the rocks. When the roasted ore is concentrated on Wilfley tables in the chlorina¬ 
tion and cyanide mills, a small quantity of white, heavy concentrate is separated, 
which proves to be zircon and doubtless is derived from the rocks in which the ore 
is contained. 

Rutile. —Occurs in microscopic form as a product of alteration of titanite, due 
to vein formation. 

Limonite. —Abundant, in finely divided form, within the oxidized zone; it 
results from the decomposition of both rocks and vein material. 

Psilomelane and wad. —Black manganese minerals are generally distributed in 
the oxidized zone as stains or filling of small cracks and fissures. Occasionally 
they form irregular masses or nodules (Summit and Pharmacist mines, Penrose). 
They are usually soft and sooty, more rarely hard and massive. These minerals 
undoubtedly result from the oxidation of carbonates containing a small percentage 
of manganese, which occur very abundantly in the veins. 

Molyhdite and ilsemannite. —In a prospect on the north side of Battle Mountain, 
near the Comanche Plume tunnel, a bright canary-yellow mineral occurs in the 

a Penrose, Mining geology of the Cripple Creek district, Colorado: Sixteenth Ann. Rept. U. S. Geol. Survey, pt. 2, 1895, 
p. 127. 




124 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

rusty cracks and joints of weathered latite-phonolite. The mineral forms micro¬ 
scopic capillary crystals, which extinguish parallel with the prism axis and have 
very strong double refraction, the minute liair-like crystals giving interference 
colors of the third or fourth order. Chemical tests by Doctor Hillebrand show 
that the material is chiefly oxide of molybdenum and that the mineral is probably 
molybdite. 

A short distance east of the Howard flat vein the Ophelia tunnel crosses a small 
vein parallel to this and located on the Anaconda property. It consists of coarse 
quartz, with comb structure, growing on a black, fine-grained mixture of pyrite, 
molybdenite, and zinc blende with a very small amount of galena and traces of 
copper and tellurium (Hillebrand). Upon exposure to the sun and air the quartz 
turns yellow or green and finally a deep prussian-blue color. Specimens soon color 
the paper of the label to a similar blue. This energetic oxidation is also shown by 
little tufts of yellow material on the specimens and occasional coatings of a dark- 
blue mammillary substance. The yellowish material is believed to be molybdite 
or Mo0 3 . The blue substance, which dissolves in water and is associated with 
some ferrous sulphate, also contains a large amount of molybdenum and probably 
is the rare mineral ilsemannite (Mo0 2 , 4Mo0 3 ), which thus far has only been found 
at Bleiberg, Carinthia, as a product of decomposition of wulfenite, while it here 
appears as a direct product of oxidation of molybdenite. 

Calcite .—Calcium carbonate is fairly common in the district, usually as a 
product of alteration in basalts or other rocks containing much lime. Microscopic 
pseudomorphs of calcite after titanite are often seen in the latite-phonolites. In 
the veins it is, on the whole, uncommon. 

Dolomite .—A dolomitic carbonate of probably variable composition is common 
both as crusts in the veins and as the product of alteration in adjoining rock. It 
has in some cases the form of the primary rhombohedron and is often slightly 
greenish in color, probably due to copper. Qualitative analyses of specimens from 
the Last Dollar mine, where the mineral is especially abundant, showed lime, 
magnesia, iron, and manganese. Dolomite crystals, replaced by opal forming 
hollow pseudomorphs, were noted from the Orpha May mine. 

Rliodochrosite .—A pink carbonate, crystallizing in rhombic forms, from the 
Fluorine mine contains an abundance of manganese and is probably rliodochrosite. 
The same mineral is abundant in the Pointer vein in veinlets up to 3 or 4 inches in 
width, crystallized with fluorite, pyrite, galena, and sphalerite. It occurs also in 
similar association in the Lead vein of the Moon-Anchor mine. 

Barite .—Massive barite in considerable amounts has been reported from 
several mines on Globe Hill. The only occurrence of supposed barite in this 
vicinity which could be examined proved to be celestite, and much of the so-called 
barite is probably celestite. Barite is, however, definitely identified from some 
of the El Paso veins, and barium (probably as sulphate) has been determined by 
analyses in the Portland ores. A small vein containing green and purple fluorite 
with tabular barite crystals occurs in granite about 4 miles south-southwest of 
Cripple Creek, near the western brink of Cripple Creek Canyon. 

Celestite .—Our attention was first called to this mineral, which is a sulphate 
of strontium, by Mr. R. H. Burrows, who stated that it occurred in a vein crossing 


GENERAL MINERALOGY OF THE DISTRICT. 


125 


the Josie S. shaft near the Humboldt prospect, at the head of Squaw Gulch. Later 
the mineral was also identified from the Wild Horse lode. Doctor Hillebrand states 
that it does not seem to be wholly anhydrous. At both places the mineral occurs 
in the oxidized zone and forms small white, bluish, or yellowish prisms and groups 
of crystals. It is directly associated with limonite and kaolin and evidently 
deposited during the process of oxidation. There is, however, a second mode of 
occurrence of celestite in Cripple Creek. In slender needles it coats the open vugs 
in the vein fissures far below the line of oxidation, and here it certainly seems to 
be one of the primary vein minerals. 

The needles are combinations of the dome (Oil) and the pyramid (144), the 
curved sides of the prisms being due to the oscillatory growth of these two crystal 
forms. The crystals resemble in habit the pseudomorphs of calcite after celestite 
found at Obersdorf, near Sangerhausen, Thuringia, and the celestite crystals of 
Mineral County, W. Va. It was identified from the C. K. & N. mine. In most 
cases these delicate needles and prisms have been transformed into acicular pseud¬ 
omorphs of fine-grained quartz, or are coated by quartz crystals, while the original 
substance has been dissolved. These are found more or less abundantly in the 
majority of veins in the district, but are especially plentiful in the Howard flat 
vein in the Ophelia tunnel, where they line a large cavity 2 or 3 feet in width. The 
pseudomorphs are found in some collections labeled cpiartz after stibnite, which 
of course is erroneous. 

A third mode of occurrence is as principal gangue in a vein on the 660-foot 
level of the Ironclad mine. The mineral is granular and partly crystallized, white 
or yellowish, and is associated with some oxidized lead ore. Here, too, celestite 
is doubtless a primary gangue mineral. 

Alunite .—This mineral was identified from level 5 of the Last Dollar mine; 
it follows the vein fissure as a rather hard and compact, fine-grained, white sub¬ 
stance, looking very much like kaolin. It was also noted from the adjoining 
Modoc mine and probably occurs at many other places. It seems to be confined 
to the oxidized zone. 

Gypsum .—Occurs in large masses in the Deerhorn shaft, associated with 
flourite and pyrite, and seems also to be fairly common in decomposed vein matter. 

Glockerite (2Fe 2 0 3 S0 3 + 6H 2 0).—This mineral was identified with considerable 
certainty by R. Pearce® in an oxidized ore from the Modoc mine. The same or 
similar ferric sulphates are probably of common occurrence in the upper levels of 
the mines. 

In the Ophelia tunnel a brown, sticky substance drips from the back and forms 
rosinlike crusts on the floor. It accumulates only during the winter. According to 
Hillebrand, it consists of a mixture of hydrous sulphates of ferric iron, alumina, zinc, 
and perhaps a little of the alkali me als. It also contains some phosphates, but no 
lime or magnesia. While essentially a mixture, it probably contains glockerite. 

Basic hydrous strontium sulphate .—This new mineral occurs as an impalpable 
white powder covering granular celestite in a vein on level 7 of the Ironclad mine, 
described on page 286. Under the microscope it proves to consist of short and 

a Further notes on Cripple Creek ores: Proc. Colorado Sci. Soc., vol. 5, 1894-1896, p. 13. 

13001—No. 54—06-10 







126 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


extremely delicate white fibers of very feeble, double refraction and an extinction 
which is probably parallel to the principal sections of the nicols. An analysis by 
W. T. Schaller of a very small quantity gave: 


Analysis of basic 

SrO. 25. 1 

CaO. 15. 1 

A1 2 0 3 . 13. 9 

MgO. 2. 5 

S0 3 . 13. 9 


strontium sulphate. 


H 2 0 (107° C.).None. 

H 2 0 (red heat). 24. 1 


94.6 


At 260°, 1.49 per cent H 2 0 was driven off, while the rest remained until red heat. 
Repeated determinations gave the same result. The analyzed material was homo¬ 
geneous. The composition is that of hydrous basic sulphate, corresponding perhaps 
roughly to CaO, SrO, A1 2 0 3 , S0 3 , 5 H,0. This is the first hydrous strontium mineral 
known to mineralogy, and as soon as its composition is satisfactorily ascertained it 
will be established as a new mineral species. 

Ghalcanthite .—Occurs very sparingly in the oxidized zone of the veins. Penrose 
mentions it from the Gold King mine in Poverty Gulch. It also occurs in the Lone 
Jack vein, Ophelia tunnel, and at several places in the Chicago and Cripple Creek 
tunnel. 

Mirabilite .—Delicate efflorescences of hydrated sodic sulphate are very com¬ 
mon in old drifts within the oxidized zone. Usually a little potassic sulphate is also 
present. It has been identified from the Anaconda-Raven tunnel and from the 
Last Dollar mine. 

Mallardite .—Efflorescences of this mineral, which is a sulphate of manganese 
with 7 molecules of water, were collected from the Moon-Anchor mine and deter¬ 
mined by Hillebrand. It contains also 2.55 per cent MgO and a very small amount 
of nickel. 

Epsomite .—Hydrated magnesium sulphate was identified from the 1,000-foot 
level of the Portland mine, but mixed with it are also some sulphates of manganese 
and alkalies. 

Other sulphates .—In the drift on the Lone Jack vein in the Ophelia tunnel, a nar¬ 
row vein in granite, the walls are coated by a white, silky, fibrous substance, which 
was determined by Hillebrand to be a mixture of hydrous sulphates of aluminum, 
zinc, ferrous iron, and magnesium. It contains no lime. Coatings of a somewhat 
similar but more massive substance of pink color proved to contain in addition a not¬ 
able amount of cobalt sulphate, to which the color of the mineral is doubtless due. 

Apatite .—Occurs commonly in the latite-phonolites as stout prisms up to 4 mm. 
long and showing prism, basal plane, and pyramid. Regarding its inclusions see 
page 74. It is also abundant as a secondary mineral in slender microscopic prisms 
with adularia in the Elkton mine. 

1 Yavellite .—A white phosphate in spherical masses of radial structure, probably 
wavellite, is mentioned by Penrose from the veins of the Raven and Bertha B. mines. 
The same mineral was found in the May mine, Arequa Gulch, and at a prospect one- 
eighth of a mile northeast of Midway station. Small amounts of phosphates mixed 
in the sulphates and various ferric silicates have been noted by Hillebrand in oxi¬ 
dized products from the Vindicator and Portland mines. 











GENERAL MINERALOGY OF THE DISTRICT. 


127 


Hubnerite. — 1 The only occurrence of a tungsten mineral noted in the Cripple Creek 
district is in the Puzzle vein on the level of Ophelia tunnel. Hubnerite, a tungstate of 
manganese and iron, appears here in a small vein associated with the zinc blende and 
galena and intergrown with quartz. It forms radial dark-brown to dark-green 
aggregates; the mineral is monoclinic, with excellent cleavage parallel to clinopina- 
coid; the striated prisms have partings parallel to an orthodome (102); extinctions 
are usually parallel to prisms, but occasionally oblique extinctions up to 17° are 
obtained. Its color in transmitted light ranges from almost opaque reddish brown 
to olive green, a single crystal sometimes showing several different colors. It is not 
pleochroic. The double refraction is medium strong, probably about 0.025. 

Titanite. —In microscopic, lozenge-shaped yellowish-brown crystals this mineral 
is common in many of the rocks of the district, notably in the latite-phonolite. 

Orthoclase.— Occurs as an important constituent in all of the rocks in the district, 
except the diabases and some basaltic dikes. It is also common as a mineral of the 
vein-forming period and has then the crystal form and composition of adularia. It is 
most abundant in the u granite ore” formed by partial replacement of Pikes Peak 
granite, but is also found in veins contained in breccia, latite-phonolite, or phonolite. 
In the granite it appears as crystalline coatings and as a true replacement. Where 
formed by deposition in open space it usually takes the wedge-shaped form charac¬ 
teristic of the variety of adularia called valencianite and is entirely similar to that 
mineral as described from Silver City^, Idaho.® The prevalent combination is the 
prism (110) and the unit dome (101). Between crossed nicols the crystals some¬ 
times show optical anomalies consisting in a peculiar arrangement of sectors, similar 
to the phenomena observed in certain kinds of vein quartz. 

Microcline. —Common in Pikes Peak granite. 

Albite. —Occurs as constituents of the granites and often intergrown with ortho¬ 
clase as microperthite. Not known in the district as a vein mineral. 

Oligoclase, labradorite, and anorthite. —These feldspars occur as constituents of 
many rocks of the district, but are much less abundant than orthoclase, microcline, 
and albite. Labradorite forms the principal mass of an anorthosite dike near the 
Galena mine. • 

Nepheline. —Occurs as an important constituent of the phonolite. 

Sodalite and nosean. —Occur as important constituents of phonolite and latite- 
phonolite. 

Analcite. —Occurs in phonolite, trachytic phonolite, and basaltic dikes, partly as 
an original constituent of the rocks, partly due to subsequent decomposition. 

Stilbite and natrolite. —Both these minerals occasionally form during the decom¬ 
position of phonolitic rocks. 

Tourmaline. —The only occurrence of tourmaline reported from the district 
is in a pegmatite dike said to occur near Rhyolite Mountain in granite. It contains 
large and well-developed crystals of this mineral, contained in quartz. 

Olivine. —Found as constituent of some of the basaltic dikes and the gabbros 
near Iron Mountain. 


o Twentieth Ann. Rept. U. S. Geol. Survey, pt. 3, 1900, p. 167. 






128 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

Amphibole .-—Hornblende occurs as a constituent of gneiss, latite-phonolite, 
and syenite; also in some basalts. It is usually of dark-brown color; a blue 
amphibole of doubtful relationship has been observed in the phonolite. 

Pyroxene .—Occurs as augite abundantly in diabase, olivine syenite, phonolite, 
latite-phonolite, syenite, and various basic dikes. iEgirine and segirine-pyroxene 
are found in the phonolites. 

Muscovite.— This mineral occurs in the granites, gneisses, and schists of the 
district. It is found as large foils in some pegmatite dikes in Pikes Peak granite, 
here occasionally of possible economic value; also as large foils in some of the schists. 
As a secondary mineral formed by the action of the vein solutions on feldspars, 
nepheline, and many other minerals, it is fairly abundant in the volcanic rocks, 
near the veins. It here takes the form of sericite, but has nowhere been developed 
on the extensive scale seen in many mining districts. 

Biotite. —Occurs as a constituent of the gneisses and granites; it is less abun¬ 
dant in the volcanic rocks. A dark-brown biotite was found as a vein mineral, 
associated with pyrite, in the Dolly Varden vein, Ophelia tunnel. Possibly this 
is the same occurrence mentioned by Penrose from the Ocean Wave claim, which 
we have been unable to locate. A green micaceous mineral allied to biotite is 
found as a product of rock alteration, probably by vein-forming solutions of 
pyroxene in many volcanic rocks. 

Roscoelite. —This light-green vanadium mica, which frequently accompanies 
rich gold ores, occurs in massive form with quartz, fluorite, and calaverite in the 
Mary McKinney mine and probably in small quantities at many other places. It 
is also believed to be present in the Lost Anna vein of the Portland mine, as well as 
in the Ajax and Stratton’s Independence mines. Iq similar association it is known 
from California gold-quartz mines, from eastern Oregon near Sumpter, and from 
the Kalgoorlie mines in Western Australia. 

Chlorite. —Chloritic minerals form rather abundantly during the alteration of 
the volcanic rocks, seemingly both by ordinary decomposition without oxidation 
and by vein-forming waters. 

Serpentine. —This mineral in no place forms large masses, but is noted as a 
product of decomposition of augite and olivine in the volcanic rocks. 

Kaolin. —Regarding this mineral Penrose says:® 

A large quantity of soft argillaceous material is found in the ore bodies in both the granite and the eruptive 
rocks throughout the district, and has evidently been derived largely from the decay of feldspar and other 
aluminum compounds. Sometimes it is stained brown by iron or black by manganese, but very often it is 
pure white. It occurs throughout the mass of many of the rocks, but is most abundant along lines of Assuring, 
sometimes simply filling cracks, at other times in irregular masses, often a foot or several feet in diameter and 
intermixed with the quartz and other vein minerals. Analyses of this material show it to have a very similar 
composition whether derived from the granite or from the eruptive rocks, and in all cases it is essentially a 
kaolin. 

Three analyses of occurrences in various rocks are given to substantiate this 
statement; in one of them, from the Albany tunnel, on the west side of Bull Hill, 
a small percentage of barite is mixed with the kaolin. A specimen from the 
Bobtail vein, Portland mine, analyzed by Hillebrand also gave almost the exact 


a Geology and mining industries of Cripple Creek district: Sixteenth Ann. Rept. U. S. Geol. Survey, pt. 2, 1895, p. 127. 







129 


% 


GENERAL MINERALOGY OF THE DISTRICT. 

composition of kaolin. Contrary to the opinion of Penrose, the kaolin appears 
to be strictly confined to the zone of oxidation, and is probably formed by the action 
of sulphuric acid on aluminous minerals. 

Clirysocolla .—Occurs as a product of oxidation of tetrahedrite on level 7 of 
the Ironclad mine and may probably be found in small quantities at many other 
places. 

Morendte {?), chloropal (?).—Within the oxidized zone a soft dark-green to 
black substance is of fairly common occurrence as the filling of seams and narrow 
veins. Upon being dried it assumes a light yellowish-brown color and proves to 
be chiefly a hydrous ferric silicate, possibly corresponding in part to chloropal and 
in part to the newly established species morencite. rt It was first observed by 
Penrose b from the Ida May mine, and has been noted by us from the Portland, 
Vindicator, and Deadwood mines. Hillebrand found the mineral from the Ida 
May mine to consist of 41.80 per cent Si0 2 , 37.20 per cent Fe 2 0 3 , 19.90 per cent H 2 0, 
and 1.10 per cent CaO, etc. Smaller amounts of carbonates and phosphates are 
often present. 

HYDROCARBONS. 

Coal .—At several places the breccia contains inclusions of coaly material, 
evidently formed by carbonization of vegetable remains carried down from the 
surface at the time of the volcanic eruptions. The character and significance of 
these occurrences have been discussed on page 31. 

aLindgren, W., and Hillebrand, W. F., Min erals from, the Cliitou-Morenci district, Arizona: Am. Jour. Sci., vol. 18, 
December, 1904, p. 455. 
t Op. cit., p. 122. 







\ 


CHAPTER V.—HISTORY AND TECHNOLOGY OF THE GOLD 

DEPOSITS. 

HISTORY OF MINING DEVELOPMENT. 

The story of the discovery of gold at Cripple Creek has been well summarized 
by Penrose/' and has been related in picturesque detail by Rickard/ The latter 
interesting account leaves, indeed, little to be added, and were it more accessible 
to most readers of this report the following sketch of the development of the dis¬ 
trict might begin where Rickard ends. 

The historic rush of prospectors to Pikes Peak in 1859 resulted in no important 
discoveries and is significant rather as the first determined attack upon the wilder¬ 
ness than from any direct connection with the history of Cripple Creek. It was 
not until 1874 that the region adjacent to Cripple Creek began to attract the atten¬ 
tion of prospectors. The report that H. T. Wood, while connected with the Hay^- 
den Survey, had found gold ore near Mount Pisgah drew a number of men to that 
locality. A few loose fragments of ore were found on the surface and the Mount 
Pisgah mining district was organized. But no valuable deposits were uncovered, 
though in 1878 Henry Cocking is said to have driven a tunnel in Poverty Gulch 
near the point where the Gold King and C. O. D. mines were afterwards developed, 
and openings were made by B. F. Requa and others in what is now the productive 
part of the district. , 

The district was then gradually deserted. There was a brief renewal of activ¬ 
ity in 1884, caused by the reported discovery of rich placer deposits near Mount 
Pisgah. The alleged discovery, however, appears to have been fraudulent, and 
the grassy hills of the Cripple Creek region, now thoroughly discredited in the eyes 
of mining men, were given over to the grazing of cattle. Traces of the pastoral 
period remain in the names of many of the hills, while in the southern part of the 
town of Cripple Creek there yet stands the log house of Bennett & Myers’s Broken 
Box ranch, long the only habitation in the region. 

The events that were destined to transform a lonely cattle ranch into one of 
the greatest gold districts in the world have been so vividly related by Rickard as 
to be best given in his own words: 

Among the earliest of the gold seekers was Robert Womack, who once owned a small ranch in the dis¬ 
trict. He sold it to Bennett & Myers, the proprietors at that time of the cattle range, which covered a 
large part of the area now forming the environs of the town of Cripple Creek. For many years, between 
1880 and 1S90, Bob Womack lived in the district, doing occasional work for Bennett & Myers and spending 
his spare time in prospecting. He had previously had some experience in Gilpin County and knew gold ore 
when he saw it. In the course of desultory diggings he found several veins, and when he would turn up at 

across, W., and Penrose, It. A. F., jr., The geology and mining industries of the Cripple Creek district, Colorado: 
Sixteenth Ann. Rept. U. S. Geol. Survey, pt. 2, 1895,'pp. 113-115. 

b Rickard, T. A., The Cripple Creek gold field: Trans. Inst. Min. and Metallurgy (London), vol. 8, 1899, pp. 49-55. 




130 





HISTORY OF MINING DEVELOPMENT. 


131 


intervals, at Colorado Springs, he exhibited pieces of float (surface ore) as evidence of his discoveries; but 
having a reputation for honesty rather than shrewdness, his statements made little impression. For many 
years he worked on a hole in Poverty Gulch without staking a claim in proper form. There seemed no need 
to do so; no one came to disturb him; the whole hill country was at that time fenced in so as to serve as a 
summer range for cattle. The cowboys and herdsmen looked good-naturedly at Bob’s digging, but did not 
consider it of any moment. In December, 1890, E. M. De la Vergne and F. F. Frisbee came up from Colo¬ 
rado Springs to prospect. George Carr, who was in charge of the ranch belonging to Bennett & Myers, showed 
them around the district. The hills were under snow, and only a few bare spots permitted of any prospecting. 
On Guyot Hill, in Eclipse and Poverty gulches, they found evidences of gold veins, and samples were taken 
away. These averaged about 2 ounces of gold per ton. Encouraged by their first visit, De la Vergne and 
Frisbee returned early in February, 1891. They found Bob Womack at work in Poverty Gulch. He had 
sunk a shaft to a depth of 48 feet, and encountered good ore. The claim he had pegged out was called the 
“Chance,” and a number of stakes indicated that he had relocated it six years in succession without record¬ 
ing the fact or complying with the conditions of the mining law in regard to the amount of assessment work 
required annually. When he found the newcomers were making inquiries he relocated the claim as the “El 
Paso,” and De la Vergne, finding another lode, heavy in iron pyrites, to the west of Womack’s vein, located 
a claim which he called the “El Dorado.” It was recorded a few days later, and in the certificate the district 
was called for the first time by the name which it still hears, Cripple Creek. Although these locations had been 
made, little actual mining was done upon them for some time afterwards. Womack absented himself. Fris¬ 
bee saw that there was a good deal of surface ore which could easily be removed, so while Womack was away, 
he sent 1,100 pounds by wagon to the Pueblo Smelting and Refining Company, who gave returns at the rate 
of $200 per ton. This was in August, 1891. Frisbee induced Womack to give him a bond and option on 
the El Paso for $5,000. Shortly afterwards it was transferred to Messrs. Lennox and Giddings, who still own 
it, as a part of a very successful mine, the Gold King. 

In May Frisbee and De la Vergne happened to be at Colorado Springs and met W. S. Stratton, to whom 
they showed certain assays of ores brought down by them from Cripple Creek. Stratton was a house builder 
and carpenter by trade, but in the intervals of his regular occupation he had been prospecting for fully twenty 
years previous to this date. He had learned the use of the blowpipe and was familiar with the outlines of 
mineralogy and geology—in fact, an energetic, well-informed man, thoroughly equipped for prospecting work 
of any kind. At that time he had been searching for cryolite, a mineral from which the metal aluminum is 
obtained, and had a camp on the Little Beaver, on the Cripple Creek side of Pikes Peak. After the meeting 
with De la Vergne and Frisbee he went to Cripple Creek and camped there. Stratton met Bob Womack and 
went around seeing the little work done by the latter and his associates. Among those who were prospecting 
in the vicinity was Dick Houghton, an old mountaineer, prospector, and specimen hunter whose labors have 
enriched many museums. One day Houghton brought down a piece of rock from the Lone Star claim on 
Gold Hill, and, meeting Stratton in Poverty Gulch, he told him he had found some galena (the sulphide of 
lead). Stratton examined it with his magnifying glass and expressed doubts as to its being galena, and in 
looking at the ore he saw little cubes of rusty gold, one of which had been scratched by being carried in 
Houghton’s pocket so as to expose a bright surface. They went down to Stratton’s tent, and he pulled out 
his blowpipe and made a test which proved that it was gold. Neither of these men knew at the time that the 
bright silvery mineral, which Houghton thought to be galena, was sylvanite—the telluride of gold and silver. 
Stratton went up and located the claim adjacent to Houghton’s; it was named the Gold King, and is now a 
part of the Gold and Globe property. On the 5th of June Stratton, accompanied by Fred Troutman, went 
to the ridge above Battle Mountain, and, seeing the willows at the head of Wilson Creek (where now the town 
of Goldfield is situated), they inferred the presence of water. They descended the hill and got a drink; then 
climbing the hill behind the spring, they found loose pieces of rock, one of which was broken open and found 
to be smothered in gold. The owner of the Independence says that this was the only time he got really excited. 
Camp was moved from Cripple Creek next day and pitched close to the spring. A search was begun for the 
lode which had shed so goodly a float. Trenches were dug; but Stratton had an idea at this time that veins 
with a north and south direction were the ones which carried rich ores, and so his trenches were dug at right 
angles to this course, with the result that they paralleled the veins actually existing there, and since developed 
into the Legal Tender, Lillie, and Vindicator mines. They found nothing. An old ranchman, Billy Fernay, 
came along about this time and brought some float which he had found on the hill below, now called Battle 
Mountain. Stratton liked the look of it, so Fernay located it for Stratton, Troutman, and himself, calling it 
the Black Diamond. It is now one of the claims included within the territory of the Portland mine. Next 


132 GEOLOGY AND GOLD . DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


day Stratton went down to see the vein and tried to make the course of it accord with the line of the ridge. 
This led him down the hill to a big outcrop of granite. It was the Independence vein, which had already 
been seen by many, including nearly all of those whose names have been mentioned. The path from one 
ranch to another went close by, and all the cattlemen who had any idea of prospecting had looked at it. ' 
Every one had condemned it as worthless granite. Fernay pointed it out to Stratton, but he also did as the 
others had done. On examining the outcrop he remarked the absence of any metallic mineral and of vein 
quartz such as he had been accustomed to in the San Juan region, and therefore concluded that it was an 
unlikely looking rock. And so it really was, for it was granite without the ordinary gold-bearing minerals 
visible in it, differing indeed from the granite of the dome of Pikes Peak in being less fresh in appearance, 
brown instead of pink, and marked by dark spots where the mica had been decomposed. Some of it yet 
remains in place, inviting the observation of those who may wonder why the great lode was so long disre¬ 
garded. Stratton overlooked it, but not irretrievably. Two days later John R. McKinnie, who was one of 
the first prospectors in the district, came to their camp, and so did Charlie Love, a ranchman from Beaver 
Park, who had pointed out the big outcrop to many of the prospectors. The latter asked McKinnie if he 
had seen it, but the matter was allowed to drop. Stratton remembered the incident when, on the morning 
of the Fourth of July, he was at Colorado Springs, whither he had gone with five samples for assay. The 
assays gave only $3 or $4 per ton at the best, notwithstanding that he had obtained good results by panning 
It suddenly occurred to him that the granite outcrop must be the lode. He had found gold in the loose frag¬ 
ments of porphyry lying upon the south face of Battle Mountain near the granite outcrop, but he had been 
unable to trace its source to any vein in the porphyry formation. Acting on the impulse, he took a horse 
immediately, and on arrival found Troutman ready to leave in order to celebrate the Fourth at Colorado 
Springs. Stratton made two locations, the Washington and the Independence. I doubt if any man ever 
celebrated the Fourth of July to better advantage. Some pieces of the outcrop of granite ore were broken, 
and Troutman took them to be assayed at the Springs, while Stratton awaited the result. Troutman returned 
on horseback next day with the assay certificate, proving the ore to be worth $380 per ton. The rest of the 
story is simple. It records the steady development of one of the richest mines ever uncovered by the miner’s 
pick. 

The development of the district, notwithstanding the fact that many mining 
men of capital and experience looked askance at what they regarded as another 
Cripple Creek bubble, was extraordinarily rapid. Before the opening of spring in 
1892 the hills swarmed with prospectors, and on February 26 the town of Cripple 
Creek was incorporated. Adjoining it on the southwest sprang up the town of 
Fremont, afterwards absorbed by Cripple Creek. The main route into the district 
at this time was by wagon road from Florissant. 

In October the Anaconda, Arequa, Blue Bell, Buena Vista, Deerhorn, Eclipse, 
Gold King, Matoa, Mountain Boy, Ophir, Pharmacist, Plymouth, Strong, Summit, 
Sweet, Victor, and Work mines were shipping ore, and railroads were under con¬ 
struction from Canyon on the south and from Divide on the north. 

In the autumn of 1893 the list of producing mines had become a long one 
and included the Blue Bird, C. O. D., Dead Pine, Doctor, Eclipse, Elkton, Gold 
Dollar, Granite, Ingham, Logan, Mary McKinney, Moose, Morning Glory, Portland, 
Raven, Stratton’s Independence, Strong, Tornado, Zenobia, and many other well- 
known properties. 

The Midland Terminal Railroad, connecting Cripple Creek with Colorado 
Springs by way of Divide, was completed December 16, 1893, and the Florence 
and Cripple Creek Railroad was opened to traffic July 2 of the following year. 

The year 1894 is memorable on account of a strike during which the miners 
resorted to arms, property was destroyed, and lives were lost. A large force of 
deputy sheriffs was finally enrolled to restore order, but at this stage the governor 
of Colorado called out the militia and put a stop to what threatened to become 


HISTORY OF MINING DEVELOPMENT. 


133 


a miniature war. The mine owners, by the “ Waite agreement,” consented to the 
establishment of a minimum wage, to the eight-hour day, and to the avoidance of 
all discrimination between union and nonunion men. In spite of these disturb¬ 
ances the development of tne district made notable strides and the Independence 
mine in particular revealed bodies of ore that were the marvel of the camp. The 
mine at this time was only 70 feet deep and was worked with a horse whim. It 
shipped in August 800 tons, of which the poorest carload averaged 31 ounces of 
gold per ton. The Portland mine at this time was shipping about 60 tons of smelt¬ 
ing ore daily. About 100 men were employed and the mine produced more ore 
than any other property in the district. It was in the latter part of this year that 
Cross and Penrose investigated the district for the United States Geological Survey. 

In 1895 the Portland mine had reached a depth of 600 feet and the Independ¬ 
ence 470 feet. The latter was the most profitable mine in the district, and Stratton, 
now a rich man, began the purchase of outlying property. The Logan and Ameri¬ 
can Eagle mines were bought by him this year and were consolidated as the American 
Eagle group. lie acquired a number of other mines in succeeding years. The 
Vindicator, 60 feet deep; the Mary McKinney, 146 feet deep; the Anna Lee, 760 
feet deep; and the Elkton, Pharmacist, Isabella, Victor, Last Dollar, Strong, 
Anchoria-Leland, Abe Lincoln, C. O. D., and Gold King were all shipping ore in 
this year, and considerable excitement was caused by the remarkably rich ore 
shoots in the Moose, Raven, and Doctor mines on Raven Hill. Several of the 
mines encountered water about this time and had to begin pumping. 

During the next few years the number of producing mines continued to increase, 
and in 1900 the maximum output of 818,000,000 was obtained. Beacon Hill 
attracted much attention in consequence of rich ore found in the Prince Albert 
and adjacent mines. The Victor and Isabella mines were highly productive up to 
1898 and 1900, respectively, and shipped large quantities of very rich ore. Four 
long tunnels, the Chicago, Good Will, Ophelia, and Standard, were begun about 
this time. In 1899 the Standard tunnel encountered a flow of water 2,800 feet 
from the portal, which compelled a suspension of operations. Teller County, with 
Cripple Creek as its county seat, was formed from a portion of El Paso County. 
Another notable event of the year was the sale of Stratton’s Independence, the 
most famous and profitable mine in the district, to the Venture Corporation (Limited), 
of London, for $10,000,000. 

In 1901 the Colorado Springs and Cripple Creek District Railway was com¬ 
pleted into the district. About this time many of the larger mines, having worked 
down to the water surface determined by the outflow through the Standard tunnel, 
were again compelled to face the question of deeper drainage. A drainage com¬ 
mission was formed, subscriptions were collected, and the El Paso tunnel was 
begun in 1903. Connection was made with the El Paso mine, under Beacon Hill, 
in the autumn of the same year. ♦ 

The year 1902 is noteworthy chiefly on account of the discovery of remark¬ 
ably rich ore in the recently opened C. K. & N. mine on Beacon Hill and the coming 
into prominence of the El Paso and Golden Cycle mines as large producers. 

Early in 1903 a strike was ordered by the Western Federation of Miners in all 
mines shipping ore to certain reduction works in Colorado City. The difficulty was 


134 • GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

adjusted for the time, but after some months of agitation and uncertainty another 
strike was called on August 10, which resulted in the closing of nearly all the mines 
in the district except the Portland. The mine owners organized and took active 
steps to reopen the mines with nonunion labor. Work was first resumed at the El 
Paso under strong guard, and some of the other mines were soon afterwards reopened 
under similar conditions. It soon became evident, however, that any general 
attempt on the part of the mine owners to work the mines would be the signal 
for violence. Governor Peabody accordingly ordered the militia into the district, 
and under their protection all of the mines gradually resumed operations with 
nonunion miners. A number of dastardly outrages, such as the murder of the 
superintendent of the Vindicator mine and the blowing up of a station platform 
at Independence at a time when it was crowded with nonunion miners, were per¬ 
petrated about this time, and, being generally charged to the union men, led to 
coercion and deportations. 

The general depression caused by the labor difficulties of 1903 and 1904 was 
partially relieved by a number of discoveries of new pay shoots, particularly of a 
body of remarkably rich ore in the W. P. II. claim, on Ironclad Hill. Ore of very 
high grade was found also in the El Paso mine and new pay shoots opened in the 
Gold Coin and Granite mines. In the Portland mine a number of new ore bodies 
were discovered, indicating that the ore reserves on several of the levels were 
larger than had been generally supposed. 

At the present time there are probably not more than ten of the really large 
mines that are operated by their owners. The Isabella, one of the most extensive 
mines in the district, is doing very little, and the great Stratton’s -Independence is 
now worked by lessees. The number of small mines in active operation is, how¬ 
ever, comparatively large, and it is to be noted that some of these small mines, 
such as the Strong, have been nearly as profitable as their larger neighbors. Leas¬ 
ing or tributing is extensively practiced, several mines of moderate size and a large 
number of the smaller properties being worked on this plan. The extensive hold¬ 
ings of the Stratton estate, which have lain idle for the past few years, have recently 
been opened to lessees and may be expected to add materially to the production 
of the district. 

PRODUCTION. 

Though situated close to the centers of population in Colorado and in an easily 
accessible region, the gold deposits of Cripple Creek were not discovered until 1891. 
To a great extent the lateness of the discovery was due to the extremely inconspicu¬ 
ous character of the vein croppings and to the equally inconspicuous appearance of 
the dark-brown, powdery gold set free by the oxidation of tellurides. As soon as 
the true character of the veins was ascertained the development of the district pro> 
ceeded rapidly. In 1894, when the first survey was made, the production was a 
little less than $3,000,000, but the next year this amount was more than doubled, 
and in 1900 the maximum production of a little over $18,000,000 was attained. In 
1901 and 1902 the production declined slowly, and dropped the next year to 
$13,000,000. The sudden decrease in 1903 was to some extent brought about by 
the impoverishment of several mines, but the labor troubles of that year had also 


HISTORY AND TECHNOLOGY OF THE GOLD DEPOSITS. 


135 


much to do with it. From August, 1903, to the summer of 1904 many mines expe¬ 
rienced more or less difficulty from this cause. 

Production of the Cripple Creek district according to the reports of the Director of the Mint.a 


Year. 

Gold. 

Silver. 



Fine oz. 

1891. 

$449 


1892. 

583,010 


1893. 

2.010,367 

5,019 

1894. 

2,908,702 

25,900 

1895. 

6,879,137 

70,448 

1890. 

7,512,911 

60,864 

1897. 

10,139,709 

57,297 

1898. 

13,507,244 

68,195 

1899. 

15,658,254 

82,520 



Year. 

Gold. 

Silver. 



Fine oz. 

1900. 

$18,073,539 

80,166 

1901. 

17,261,579 

90,884 

1902. 

16,912,783 

62,690 

1903. 

12,967,338 

42,210 

1904. 

14,499,529 

55,790 

1905. 

15,724,344 

35,643 

Total. 

154,638,895 

737,626 


a The figures given in the mint reports are considerably lower than those usually quoted in mining journals and popular 
descriptions of the district. 


The total dividends can not be ascertained on account of the many individuals 
and small companies operating in the district. The dividends of the larger com¬ 
panies, it is stated, amounted to $32,752,000 to the end of 1903. In that year it is 
reported that $1,716,000 was paid by fourteen mines, the Portland, Strong, and 
Stratton’s Independence leading, with $360,000, $300,000, and $250,000, respec¬ 
tively. 

The annual tonnage of the camp has probably not exceeded 700,000 short tons 
of ore. For the year 1904 it was nearly 600,000 tons. Of this, the Portland mine 
produced about one-sixth. 

The distribution of the total tonnage of ore over the several parts of the district 
varies, of course, from time to time. An investigation made in 1903 for the Cripple 
Creek Times shows that 42.7 per cent came from the Battle Mountain mines, 30 per 
cent from Bull Hill, including the Vindicator lode sj^tem, 7.4 per cent from Raven 
Hill, '5.8 per cent from Beacon Hill. 7.8 per cent from Gold Hill, and 4.9 per cent 
from Guyot Hill (including the Man" McKinney mine). Since that time the out¬ 
put from Beacon Hill has increased considerably and that from Bull Hill is probably 
somewhat less. 

MINING. 


The methods of mining employed at Cripple Creek are not materially different 
from those in use in other districts where metalliferous veins are exploited. Over¬ 
hand stoping with slightly differing variations is used. In narrow veins short 
stulls comprise about the only timbering used and required, but when the stopes 
become over 12 feet wide square sets become desirable. The rock is usually so hard 
that stopes will stand unsupported for a remarkable height and width. Examples 
of stopes up to 200 feet high and 30 feet wide standing without any support may be 
seen at the Vindicator and Prince Albert mines. Still in many places the calcite 
seams cause a dangerous scaling off on the walls, and partial filling must be resorted 
to in conjunction with the square sets. In the big stopes up to 50 feet wide, as in 
the Portland mine, from 30 to 40 per cent of the total amount broken can be left in 
the mine as filling. 


































136 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


A favorite method of stoping is to break down the whole of the ore in place 
between two levels, leaving the loose rock to be drawn off through shoots as rapidly 
or slowly as may be required. This leaves the empty stope entirely unsupported. 
Sometimes the walls are partly secured by stulls while the ore is being drawn off. 
The ordinary half or three-fourths ton cars are used. The El Paso is the only mine 
in which 1-ton cars have been introduced and hoisted on cages. Buckets are also 
employed very extensively in the shafts and sometimes used to a depth of even 
1,000 feet, a practice which is not to be recommended. Practically all of the shafts 
are perpendicular. The hoisting is generally effected by steam; electric power is 
used in winzes and small shafts. The Portland is the only mine which has installed 
self-dumping 3-t.on skips into which the contents of the cars are directly charged at 
the various levels. At this mine the waste is disposed of into side-dumping cars 
taken to the dump by rope haulage. 

In treatment and sorting of the ore at the mines various plans have been 
adopted. The general occurrence of friable tellurides in cracks and fissures forms the 
principle upon which the sorting and separation is based. The fines are invariably 
much richer than the coarse stuff, and the separation of the two classes becomes of 
importance. The ore is usually broken on plank floors with canvas underneath to 
avoid loss of the fine material. A rough preliminary sorting is effected in the mine—- 
at least in places where wide stopes are being operated. The further treatment 
varies in the different mines. Very rich ore containing from 4 ounces upward is 
usually sacked and sent to the smelters. At the Portland mine the following 
process is adopted, the scheme being outlined in the eighth annual report of the 
company by Mr. Charles J. Moore, formerly its consulting engineer, as follows: 

Crude ore. 


Milling ore, Mill dirt, Waste, 

$15 to $60. $5 to $15. below $5. 
















HISTORY AND TECHNOLOGY OF THE GOLD DEPOSITS. 


137 


The ore from the various stopes is not separated but dumped in two bins after 
passing over 1-inch grizzlies. The hand sorting is done at six tables with four 
men at each. The waste from the sorting,slides down over an inclined 15- by 4- 
foot sheet-iron plate perforated with half-inch holes and is continually sprayed in 
order to wash off the fines. Before going to the dump the waste from the washer 
is finally picked over on a belt conveyor. 

At the Mary McKinney mine the ore from the stopes is shoveled into a Crane 
washer, a local invention composed of a 46-inch by 15-foot trommel with three- 
fourths inch holes, separating out the dry fines. The coarse is discharged into a 
smaller strongly inclined and perforated trommel about 15 feet long, the near end 
partly submerged in a tank of water. By this device the ore is washed, the fines 
falling into the tank and the coarse being carried up by means of an endless screw 
and discharged at the higher end of the trommel on a conveyor belt 50 feet long 
and 20 inches wide, on which the ore is sorted by five men. The capacity is said 
to be 100 tons per eight hours. 

At the El Paso mine ten bins are used and the ores from various stopes are 
kept apart. The classification is effected by two or three parallel screens under a 
protecting 3- by 15-foot grizzly, with bars 4 inches apart. The first screen has 
1-inch perforation, the second three-fourths inch. The dry fines below three- 
fourths inch average $75 per ton, those between 1 inch and three-fourths inch $25. 
From each bin the ore slides down on a sorting table, while sprays wash off the 
remaining fines, which are collected in tanks. These fines are of very high value. 
Ten sorters are employed. The present output (March, 1904) is 50 tons per day. 

In former j^ears the sorting of the ore was much neglected, as evidenced by 
the numerous rich dumps in the camp. Even now the arrangement at many 
mines is imperfect. 

The cost of mining is, as a rule, very high, though few accurate data are avail¬ 
able on this subject. Mr. J. R. Finlay/' the former manager of the Portland mine, 
makes the following statement, which is well worth quoting: 

A study of the situation shows that these high costs result from the amount and character of the waste 
that must be handled with the ore. As is well known, the largest ore bodies of Cripple Creek are not solid 
masses of uniformly valuable mineral, but contain volumes of rock into which the gold-bearing solutions have 
penetrated along multitudes of crevices. The problem of getting the best results in such veins is essentially 
one of concentrating the values. The peculiar character of the ore renders concentration difficult, if not 
impossible, by any method other than hand sorting. Ordinarily the concentration of ores may be effected 
cheaply by mechanical means, depending on the difference in specific gravity between the valuable and the 
worthless minerals. In the case of Cripple Creek ores this difference can not be depended upon. When the 
rock is blasted, a large part of the valuable material in the seams is reduced to an extremely fine powder, 
practically the lightest part of the mass; another part of the values will adhere to the rocks, while another 
small part is probably heavier than the average. 

The total cost of mining, including sorting and development work, is probably 
nowhere in the district—in the deep mines—less than $8 per ton and in many 
cases it may be considerably higher. The actual stoping cost in the Portland 
mine averaged about $3 per ton in 1902, and for 1903 is reported as averaging 
$2.19. 


a Ninth Ann . Rept. Portland Gold Mining Company, p. 16. See also Finlay, J. R., Mining costs at Cripple Creek: Eng. 
and Min. Jour., November 21, 1903. 






138 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

SAMPLING. 

The sampler, in the western mining regions, is the recognized middleman 
between mine and reduction works. His services have been found particularly 
acceptable at Cripple Creek on account of the richness of the ore and the corre¬ 
sponding difficulty of obtaining an agreement between smelter and miner. The 
leasing system in vogue has also helped the sampling works by multiplying small 
parcels of ore which must be separately handled. A modern sampling mill is 
quite a complicated affair, especially where rich ores render extra care necessary, 
and it is sometimes arranged to run almost automatically. Even large mines use 
the services of samplers, the Portland and the Woods Investment Company being 
the only ones possessing mills of this kind for their own exclusive use. The 
charges, not including freight, run from 60 cents to $1 per ton. The principal 
sampling mills working at present in the district are the Cripple Creek, the Rio 
Grande, the Eagle, and the Taylor & Brunton. 

The last, situated in the gap between Bull Cliff and Big Bull Mountain, is 
the most modern plant and a brief description of its process may be of interest. 
The ore is shoveled from the car into a bin from which it goes to crusher and coarse 
rolls (42 inches). An automatic elevator carries it to the top of the building to 
36-inch rolls, below which an automatic sampling machine, by alternately deflect¬ 
ing the stream of crushed rock, cuts out 20 per cent of the total material. This 
20 per cent goes to 27-inch rolls, below which a second sampling machine cuts out 
20 per cent, the operation being repeated underneath the third (20-inch) rolls. All 
of the rolls have automatic feeders. The total sample now amounts to 1 per cent 
of the total amount and has been crushed to about one-sixteenth of an inch in 
average size. If necessary, in large lots of ore comprising several cars, this is 
further reduced by hand, with the implement known as a “split shovel,” to about 
0.08 per cent of the original lot of ore. The sample, which now weighs from 20 to 
50 pounds, is dried and crushed fine in a rotary grinder and further reduced by 
means of the “split box” to about 30 ounces. The final pulverizing is accom¬ 
plished by means of the bucking board and a 110-mesh screen. A smaller splitter 
divides it into four parts which make the final samples. One of these is assayed 
at the sampling works, another is sent to the shipper, while two are held in reserve 
in case of disagreement between the sampler and the smelter. 

PROCESSES OF REDUCTION.' 

The history of the development of the present processes of reduction for the 
Cripple Creek gold ores is in many respects of great interest.® Stamp milling, long 
the recognized mode of treatment of gold quartz, was first tried. During 1892 and 
1893 ten stamp mills of the Gilpin County type with slow drop and light stamps 
were erected, aggregating 270 stamps, the largest being the Rosebud and the Gold 
and Globe mills, having, respectively, 60 and 40 stamps, both situated along Cripple 
Creek below the town. A short trial sufficed to demonstrate their inefficiency to 
deal with the free gold, on account of difficulties of amalgamation due to a tarnish 
supposed to be tellurite of iron. Percussion tables and blankets were introduced 

a For a full account of the early attempts to reduce the ores see Rickard, T. A., The Cripple Creek gold field: Trans. Inst. 
Min. and Metallurgy, vol. 8, London, 1899. 





/ 


PROCESSES OF REDUCTION. 139 

to improve the gold saving, but even then the extraction was lamentably low. The 
matter was made worse by the appearance of unoxidized tellurides and in a few 
years this process was entirely abandoned. 

Smelting was early recognized as a proper method of treatment for rich ores, 
and an increasing amount of such material soon found its way to the smelting 
works at Denver and Pueblo. At the present time probably one-sixtli of the 
tonnage—roughly 100,000 tons—is thus disposed of; but as ores below 4 ounces 
of gold per ton rarely go to the smelters it follows that their production is a very 
considerable part of the total output of the district. The smelting charges range 
from 86.50 upward, but vary somewhat from time to time. 

The first chlorination plant was erected by Edward Holden in 1893, and bv 
January, 1895, the first well-designed mill, of 50 tons daily capacity was completed 
at Gillett, a few miles northeast of Cripple Creek. The process employed was 
the barrel chlorination used in South Carolina and the Black Hills. 

About the same time experiments were made with the cyanide process, the 
first mill being erected at Brodie in 1892. In 1895 the Metallic Extraction Com- 

o 

pany’s mill was built near Florence and gradually enlarged to a capacity of 170 
tons per day. At that time began the struggle for supremacy between the chlori¬ 
nation and cyanide processes, from which the former appears to be emerging 
victorious. 

Another change soon began to be apparent. With the advent of improved 
railroad facilities the lower valleys were found to be better adapted for the location 
of great reduction works, Colorado Springs and Florence being the most favorable 
points selected. In 1899 there were still four plants in operation at Cripple Creek, 
but in 1903 only one mill was active, aside from two smaller plants, for direct 
cyanide work. 

In 1904 the different plants were located as follows: 


Cripple Creek: , Tons capacity. 

Economic mill (chlorination). 300 

Homestake mill (direct cyanide). 200 

Sioux Falls mill (direct cyanide). 100 

Colorado Springs: 

Portland mill (chlorination). 300 

Telluride mill, General Metals Company (chlorination). 300 

Standard mill, United States Reduction and Refining Company (chlorination). 4.50 

Florence: 

Dorcas mill (cyanide). . 1-50 

United States Reduction and Refining Company (chlorination). 400 


This makes a total capacity of over 2,200 tons, or about 800,000 tons per 
year, which considerably exceeds the greatest tonnage yet produced in the district. 

The charges of the cyanide and chlorination mills vary with the tenor of the 
ore. The cheapest schedule issued in 1904 ranged from 85.50 per ton for half¬ 
ounce ore to 89 per ton for 3- to 5-ounce ore, the freight charges from mine to mill 
being included. Recently, however, it is understood that these prices have been 
raised. The schedule in 1903 varied from 87.50 for half-ounce ore to 813.50 for 
5-ounce ore. 











140 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


The cost of treatment is somewhat difficult to arrive at, as few figures are 
published. The Portland mill places the cost of chlorination at about S3.70 per 
ton. Mr. T. A. Rickard states that in one of the large mills the cost reaches S3.46, 
which will probably be increased to S4 per ton with charges for depreciation and 
general expenses added. Roasting alone costs from 45 to 60 cents per ton (Rickard). 
In the opinion of some able metallurgists the cyanide process is much better adapted 
to the ores and will eventually displace chlorination; they claim that the cost 
should not exceed $2.50 per ton, including amortization of capital invested." 

Cyaniding without roasting is practiced in two mills at Cripple Creek which 
handle low-grade and entirely oxidized ores. In this case mining costs are low 
and ore containing $5 per ton should yield a fair profit. The extent of these ore 
bodies, chiefly located on Globe and Ironclad hills and at Copper Mountain, is as 
yet more or less problematical. The breccia is thoroughly oxidized on Globe 
Hill, in places to a depth of over 800 feet, and it is not impossible that good-sized 
ore bodies of low grade may be encountered in this vicinity. Up to date the 
fairly extensive exploration has not been rewarded by corresponding development. 6 

TECHNICAL DETAILS. 

At present the Dorcas mill, at Florence, is the only cyanide plant treating the 
ordinary telluride ores. Much of the ore is of remarkably high grade, averaging 
4 ounces per ton; it is largely obtained from the C. K. & X. mine. After passing 
through rock breaker, three sets of rolls, and a drier the ore is roasted in a Holthoff 
automatic oil-burning furnace, from which it is conveyed to bins. There are 
twelve 140-ton steel leaching tanks about 30 feet in diameter. The solution 
used is naturally strong, the different grades ranging from 0.6 to 0.8 per cent. 
The percolating gold solution is precipitated in boxes with zinc shavings. Tailings 
are passed over Wilfley tables, on which a considerable amount of coarse gold is 
saved. 

The different chlorination plants use practically identical processes. 

A type is the Standard plant of the United States Reduction and Refining 
Company at Colorado City, which treats Cripple Creek ores exclusively, has a capacity 
of 450 tons per day. All the ore received goes to the sampler. The ore is there 
crushed to three-fourths inch mesh and one twenty-fifth of it taken out for finer 
crushing and quartering for the assay and analysis sample. Belt conveyors take 
the ore from the sampler to the bedding room, where it is loaded from hoppers into 
cars and thence dumped in heaps on the bedding floor below. With ore of ordinary 
grade sufficient homogeneity of the mixture is secured by dumping alternately 
on different heaps small carloads from different shipments. But high-grade ores 
are mixed more carefully with those of lower value. 

From the bedding floor the ore is taken b} T belt conveyors to the driers—long 
tables where the ore is moved by mechanical rakes and heated only sufficiently to 
drive off mositure. It is next trammed to hoppers, whence it goes to the rolls to 

a Argali, Philip, Chlorination r. cyanidation: Eng. and Min. Jour., November 24,1904. For further contributions to the 
same subject see Greenawalt, W. E., Eng. and Mm. Jour., October 27, 1904; and Doveton, G. D., The metallurgy of 
Cripple Creek, Colo.: Min. Jour. (London), December 23, 1905. 

b At the end of 1905 five small plants with individual capacities up to 150 tons were in operation. 







HISTORY AND TECHNOLOGY OF THE GOLD DEPOSITS. 


141 


be crushed to about 20-mesh size and then fed into the roasters. These are of the 
Holthoff-Wethey type, have a capacity of 100 tons per day each, and employ an 
average temperature of about 1,600° F. The roasted ore is cooled in its journey back 
underneath the furnaces, and is then conveyed on an inclined belt to the barrel house, 
where it is loaded into hopper cars and finally charged into the chlorination barrels. 

The 10 barrels, of a capacity of 10 tons, are about 20 feet long and 5 feet in 
diameter. The exact composition of the lixiviating solution is not made public, 
but it consists essentially of a solution of electrolytically generated chlorine in water. 
The strength of the solution used is determined not so much by the value of the 
ore as by the composition of the gangue. About 100 gallons of the solution are 
used for each ton of ore, and this amount contains 1 to 2b pounds of chlorine. 

When the barrels have been charged with ore and solution, they are sealed 
and rotated for two or three hours, at the end of which time a valve at the bottom 
of the barrel is opened and one at the top is connected with water pressure. The 
solution is thus made to pass through an interior filter of the Sloan type, and the 
pulp is washed for two to four hours. About 100 gallons of water per ton of ore are 
added during the washing, making the total bulk of gold-bearing solution about 200 
gallons for each ton of ore. After the pulp is sufficiently washed the manhead is 
removed from the barrel, the barrel is rotated, and the pulp emptied into a launder 
by which it is conveyed to Wilfley tables on a floor beneath. There are 20 of these 
concentrators, arranged in batteries of 5. The headings from four of the five pass 
to the fifth, and the concentrates from this table, which represent about one two 
hundred and fiftieths of the total pulp, are saved and sent to the smelters. They 
have a value of $20 to $30 per ton. For the presence of the greater part of the 
gold in them the following explanation is offered: When the ore is roasted, pyrite 
is oxidized and converted partly into magnetite (Fe 3 0 4 ), which is only slightly 
attacked b} 7 the chlorine solution. Any gold which may have been inclosed in t^he 
pyrite is thus protected from the action of the solvent, and without concentration 
would be lost. Besides magnetite other iron oxides and barite are noticeable con¬ 
stituents of the final concentrates, and a molybdenum mineral is said to be present 
at times. Finely divided free gold is occasionally seen on the last table. 

After passing through the filters the lixiviating solutions together with the 
wash water pass to the sand boxes where the coarser sediment which has escaped 
the filter quickly falls and is returned to the barrels; then to the settling tanks, 
where they remain for eight hours and allow practically all the material in suspen¬ 
sion to separate out. During this time a gelatinous precipitate, said to be a basic 
aluminum silicate, forms and falls to the bottom. On account of the difficulty 
of washing this precipitate thoroughly, a small loss of gold may take place. 

From the settling tanks the solution is drawn into lead-lined monte-jus, and 
thence forced by air pressure into precipitating tanks. Into these the precipitating 
agent, hydrogen sulphide, is introduced direct from the generator. Precipitation 
is continued until tests show no more gold in solution, the time required being 
thirty to forty minutes. After the precipitate settles the supernatant liquor is 
drawn off and run through filter presses, and before leaving the building is passed 
through a sand filter to counteract possible leakage or breakage of these presses. 

13001—No. 54—06-11 



142 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

When sufficient precipitate has collected at the bottom of the precipitation 
tanks, it is drawn into a small monte-jus, and forced through the filter presses, of 
which there are six. Finally the presses are cleaned and the precipitate is dried, 
roasted, melted with flux, and cast into bricks. On ores of average grade an 
extraction of about 95 per cent is obtained, but since the actual loss approaches a 
constant amount, the percentage of recovery is higher for rich ores. 

Chlorine for the solution of the gold is generated electrolytically at the plant. 
A hot saturated solution of salt is treated in McDonald cells, the chlorine being 
piped away and the concentrated caustic-soda solution collected as a by-product. 

Among the principal mines from which this mill treats ores are the Abe Lincoln, 
American Eagle, Elkton, El Paso, Findley, Golden Cycle, Shurtloff, Strong, Theresa, 
and Vindicator. In April, 1904, the plant was handling about 250 tons daily. 

At the Florence plant of the same company the practice is similar, except 
that six Pearce turret furnaces are used instead of the Holthoff type. 

In the Telluride mill of 300 tons daily capacity Holthoff furnaces are used. 
The chlorine is generated by calcium oxychloride and sulphuric acid. The liquor 
from the filter presses passes through a box of finely divided charcoal and a further 
saving of 0.005 ounce of gold per ton of solution is thus effected. The chlorinated 
pulp is not concentrated at this plant. Among the mines which ship ore to the 
Telluride mill are the Ajax, Dillon, Mary McKinney, and Old Gold. 

The Economic mill at Victor, with a capacity of 300 tons, roasts after crushing 
in seven Argali furnaces and one Pearce furnace, both burning crude Florence oil. 
The chlorination takes place in seven 20-ton lead-lined revolving barrels, 171 by 8 
feet. Chlorine is generated by sulphuric acid and calcium oxychloride. The 
agitation occupies three hours. The filtrate goes to settling tanks and thence to 
five steel precipitating tanks 8 by 16 feet. Hydrogen sulphide is the precipitant 
used. After passing through filter presses the cakes of gold sulphide are roasted in 
shallow iron pans, mixed with flux, melted in a wind furnace in large graphite 
crucibles, and the gold finally poured out in 700-ounce bricks. 

The latest mill to be built is that of the Portland mine at Colorado Springs. 
This includes a sampling department with adequate dust collectors. Ore beds are 
made up of 3,000 tons capacity, the ore being reduced to three-quarters of an inch 
in size. There are three Pearce and one Holthoff roasting furnaces, originally 
built for oil burning, but now preferably heated by producer gas. Otherwise the 
practice corresponds to that already described. 

LABOR CONDITIONS. 

The minimum wages for ordinary miners are $3 a day of eight hours, and 
machine men receive ordinarily $4 to $5 a day. The total number of men employed 
by the mines and samplers was about 5,500 in 1903, and more than this were probably 
employed in 1900 and 1901. The aggregate monthly pay roll of the camp amounts 
to $600,000. By far the greater number of men, probably about 3,000, are working 
on Battle Mountain and Bull Hill. The miners are chiefly Americans, comparatively 
few foreigners being employed. 

With fair wages, a healthful climate, and comparatively cheap living expenses 
there would seem to be no reason for such labor troubles as have twice afflicted the 


HISTORY AND TECHNOLOGY OF THE GOLD DEPOSITS. 


143 


district, in both cases originating in questions relating to labor unions. The big 
strike of 1894 ended in a compromise establishing the present scale of wages and 
hours of labor. The second great strike of 1903 and 1904, begun by the Western 
Federation of Miners on the basis of seemingly irrelevant issues, was unfortunately, 
like the first, accompanied by much bloodshed and violence and ended in the defeat 
of that organization. 

FINAN(TAL CONDITIONS. 

Most of the mines of Cripple Creek were located by prospectors and working 
miners. Extensive consolidations have since taken place, but the camp still largely 
remains an aggregate of many small mines. Most of the mines paid for their own 
development almost from the grass-roots. The total number of working companies 
is probably not far from 250, while the number of mines recorded on the map accom¬ 
panying this report is 324. The owners of individual claims have usually developed 
their property themselves if they proved payable from the start. If not, a company 
was organized with the financial aid of some local man of means and, if necessary, 
some stock sold until the mine was put on a paying basis. If success did not attend 
the efforts, promising parts of the claim were leased to working miners or to small 
companies of men who were able to work more economically than a larger organi¬ 
zation. A vast amount of “wild-catting,” or organization of companies based upon 
some probably worthless piece of ground, has also been practiced, chiefly by a class 
of promoters who are always to be found in newly discovered and rich mining camps 
and to whom the gullibility of the distant public offers attractive vistas of illegiti¬ 
mate profits. Some companies consolidated to larger corporations or were sold to 
foreign capitalists, but the list of foreign-owned mines is a small one. The leasing 
system built up as a result of all these conditions has perpetuated itself and is still 
in extensive practice. The leases run from six months to two years and the royal¬ 
ties are usually 15 to 35 per cent of the net return, that is, of the sum obtained from 
the sale of the ore after subtracting transportation and reduction charges. Occa¬ 
sionally several lessees will work in one mine, each having a separate level or vein 
to work on. In one case 14 sets of lessees were at work on one small property of 
two claims. While this system may have some advantage, its drawbacks are con¬ 
siderable; it is, as Mr. T. A. Rickard says, “the last resort of a perplexed mine 
owner, and is a confession of inability to work one’s own property.”" Moreover, 
the expiration of the lease usually leaves the mine in a very unsatisfactory condition. 
The leasing system at Cripple Creek has recently been discussed by Mr. J. W. Finch, * 6 
who concludes that under certain conditions which prevail in Cripple Creek it is of 
considerable advantage. 

In organizing the mining companies of Cripple Creek a very large nominal 
capital is the nde, regardless of the size or the character of the property. In general 
it is $1,000,000 or $1,500,000, divided into shares of the par value of $1. If the 
property is a small one the value of each share is of course only a few cents; indeed, 
if it is a mere prospect the shares may be quoted as low as $1 per thousand. Practi¬ 
cally all of the stock is nonassessable and this is one of the reasons for the excessive 
capitalization practiced. A large amount is usually held as treasury stock and sold 


a The Cripple Creek gold field: Proc. Inst. Min. and Metallurgy, London, 1899, p. 39. 

& Mining Mag., vol. 12, No. 6. 



/ 


144 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

for what it may bring in case more money for development is needed. Another 
motive for overcapitalization is that every prospecting company feels that it may 
some day by rich discoveries attain the dignity of a mine, and that it will then be 
ready to do business on a great scale without reorganization. A further advantage 
from the stock-market point of view is likewise apparent; but when all is said the 
fact remains that this mode of financiering is objectionable, chiefly because of the 
false impressions created. A worthless prospect may easily be given, in the eyes of 
persons not familiar with such devices, a semblance of importance which it is far 
from possessing. 

The official manual of the Cripple Creek district, published by-Mr. Fred Hills in 
1900, contains a very complete record of the mining companies organized to work 
properties in the district. It describes the properties of 500 companies, about 100 
of which have a production of over $2,000 to their credit. Among the few companies 
with a reasonable capitalization is the Strong, with 500,000 shares at $1 and a heavy 
production, while the highest capitalization is that of the Colamokas Gold Mining 
Company, with 5,000,000 shares at $1, the production apparently being nil; also the 
Greater Gold Belt Mining Company, with the same capitalization and a very small 
output, and the Stratton’s Independence (Limited) with the same capitalization, a 
production of $7,500,000, and dividends of $4,000,000. The average capitalization is 
$1,250,000, most companies being organized with at least $1,000,000. Very few 
mines have yielded the amount of their capitalization in dividends. It is readily 
seen that few mines will be able to pay adequate dividends on this excessive capi¬ 
talization. Fortunately the capitalization is imaginary, not real, and thus it hap¬ 
pens that many of the gold mines of Cripple Creek are in a healthy condition and 
decidedly remunerative. 

The value of a mine is measured by the price of the stock. Here again the 
tendency to booming and exaggeration incidental to excessive capitalization has 
made itself felt in higher prices for stock than were warranted. Since 1900, how¬ 
ever, the prices have receded and now probably more nearly approach the true 
value, based on ore in sight plus an amount varying with the probable prospects of 
the mine. From the present share prices ($1.70) the Portland mine is now worth 
$5,000,000, whereas a few years ago the valuation reached $9,000,000. Stratton’s 
Independence at present prices (1905) is valued at $620,000, whereas in 1899 it sold 
for about $11,000,000. The Elkton at present prices would be worth $1,250,000. 

It might seem that a high production would justify a very large valuation. 
Many people, however, lose sight of the fact that the majority of gold mines have a 
limited life and that a large interest is necessary to recover the capital, together with 
an adequate return from the venture. 

To illustrate the manner in which many of the mines have grown, the Portland 
may again serve as an example, though few properties have been as successful as 
this. The Portland was located as a small claim in 1892 by three prospectors. 
A year later some rich ore was stoped. The development continued on a small scale, 
and in 1894 the present company was organized with a capital of $3,000,000. Rich 
ore was found, and in the next few years the proceeds were diverted to the purchase of 
adjoining claims, until in 1899 the whole present area of 200 acres had been acquired. 
Meanwhile the mine also paid for the erection of plants and all other necessary 




HISTORY AND TECHNOLOGY OF THE GOLD DEPOSITS. 


145 


expenses, including a large mill built in 1902. The mine is now in an enviable posi¬ 
tion. It is said that not one share of treasury stock was sold for purposes of mine 
development or equipment. 

The English companies which have ventured into the Cripple Creek field have been 
notably unfortunate. The Lillie Gold Mining Company (Limited) was capitalized at 
$1,125,000 and had yielded $360,000 in dividends when it was found that the shoot 
pitched into the adjoining ground. On the basis of the moderate capitalization 
which the small area of only 7 acres would have justified, this should have been a 
successful undertaking. The Stratton’s Independence (Limited) was bought, with 
$5,000,000 profits in sight, for $11,000,000 and capitalized for £1,000,000 in £1 
shares, the value per share at the time of flotation being about $10; from 1899 to 
1904, inclusive, $7,500,000 have been produced and $4,000,000 paid in dividends. 
The Moon-Anchor Consolidated Gold Mine (Limited) has also an unsuccessful record. 

It can not be said that any record-breaking results have been achieved in Cripple 
Creek in the way of economic treatment of the ores. In fact, compared with that in 
many other districts, both in the United States and in foreign countries, the expense 
of mining and milling seems extraordinarily high. The combined cost of mining and 
milling in the large mines ranges from $15 to $25 per ton. At Kalgoorlie, Western 
Australia, where similar ores and conditions prevail, the total cost had several years 
ago been reduced to $10 per ton and is now still further reduced to about $7.50 
per ton. 

There are several factors entering into this problem. One relates to imperfect 
sorting and washing of ore, now less in evidence than formerly. The many rich 
dumps of supposed waste, profitably washed over again, testify abundantly to neglect 
in this direction. On the other hand, careful hand sorting will materially increase 
the cost of mining, though at the same time it may result in gr.eater profits.® There 
has undoubtedly been great carelessness in mining, as is shown by the profits made by 
tributers in old stopes. The Cripple Creek ores are much more friable than those of 
Kalgoorlie and loss by fines is much more apt to take place. Free gold is present in 
the Western Australia ores in varying amounts, while almost wholly lacking in 
Cripple Creek. The Diehl process used at Kalgoorlie includes a preliminary concen¬ 
tration on Wilfley tables, roasting and cyaniding of concentrates, and agitation with 
bromocyanide of the tailings from the tables. This does not seem to be directly 
applicable to Cripple Creek ores. But of even greater importance are the heavy 
charges for ore reduction, which, for very commonly occurring ores of $40 per ton, 
amount to from $8 to $13 per ton, inclusive of freight. To a great extent this is 
caused by the presence of many small operators, who can not afford to build reduc¬ 
tion works themselves and who naturally avail themselves of the advantages of the 
custom mill. The large mines mostly followed the example of the smaller contingent. 
The rich ores were there in sight awaiting extraction; the stockholders were awaiting 
their dividends. Why bother about a few dollars per ton when a custom mill was 
available ? This seems to have been the line of reasoning of many large companies who 
doubtless would have made much more money by waiting a little while and building 
their own reduction works, not necessarily on a very large scale. There is no doubt 


a Finlay, J. R., Eng. and Min. Jours November 21, 1903. 




146 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

that it is of advantage to “rip” the ore out of a mine as rapidly as possible, short of 
“robbing the mine,” but there is also such a tiling as dividing profits a little too 
liberally with reduction works and railroads. 

EXTENT OF PRODUCTIVE TERRITORY. 

There is nothing in the history of the district since 1894 warranting any exten¬ 
sion of the bounds of the productive territory as then known. Now, as then, a circle 
of 3 miles radius described from the summit of Gold Hill would include all deposits of 
known or prospective value, while the really important mines would be embraced by 
a circle of about half that radius, with its center near the summit of Raven Hill. 
That scattered deposits of greater or less value may be found in outlying portions of the 
district is by no means improbable. But the close dependence of the typical Cripple 
Creek ores upon the main volcanic center and the consequent remarkable compact¬ 
ness of the gold-bearing area are features highly characteristic of the district and are 
likely always to remain so. 

The greater part of the ore has undoubtedly come from the central area of breccia, 
particularly from that part of this area in which the breccia extends to great depth. 
Very productive ore bodies have been found, however, in the granitic rocks, usually 
within 1,000 feet of the steep contact limiting the breccia on the southwest. The 
important Beacon Hill mines, with ore bodies nearly three-fourths of a mile from this 
contact, are exceptional, and are probably genetically connected with the intrusive 
mass of phonolite forming the core of the hill. 


> 


CHAPTER VI—PRELIMINARY REVIEW OF THE MINING INDUSTRY. 


EARLIER WORK IX MIXING GEOLOGY. 

To the excellent work of R. A. F. Penrose, jr., apply statements similar to those 
made in the discussion of the purely geological branch of the subject. Few shafts 
had then attained a depth of 400 feet, and most of the exposures were marked by 
surface oxidation. It would be surprising, in view of the facilities created by the 
later development of hundreds of mines, if a subsequent investigation should not 
bring out some slight modifications of earlier results. 

DISTRIBUTION OF MIXES. 

The productive district, as previously stated, is practically covered by the area 
of a circle 34 miles in diameter. The center of this circle would be located halfway 
between Raven Hill and Bull Hill, and the towns of Cripple Creek, Victor, and 
Cameron would be situated on its periphery. A very few mines—notably the Galena 
and the Fluorine—and many prospects lie outside of this area. 

The culminating points of the district are found in a ridge of high and bare hills 
that extends in a northwest-southeast direction and divides the waters flowing into 
Cripple Creek and Wilson Creek on the southwest from those joining Spring Creek 
and Grassy Creek on the north. From northwest to southeast the following hills 
mark this divide: Mineral Hill, Carbonate Hill, and Tenderfoot Hill, north or north¬ 
east of Cripple Creek; Globe Hill, Ironclad Hill, and Bull Hill, the latter being near 
the center of the district and equidistant from Cripple Creek and Victor. The ridge 
is continued by Bull Cliff and Big Bull Mountain, the latter, really outside of the 
product ive area, being the highest point in this dividing range of hills. Its elevation 
is 10,826 feet. Three long spurs project to the southwest from the dividing range 
separating the deep trenches of Cripple Creek, Squaw Gulch, Arequa Gulch, and 
Wilson Creek; the first, called Gold Hill, rises directly east of Cripple Creek; the 
second is Raven Hill, being continued to the southwest by the lower spur of Guyot 
and Beacon hills; the third is Battle Mountain, continued by the almost equally 
high salient of Squaw Mountain. 

The important mines are situated in this region of sharply accentuated topog¬ 
raphy. As has been several times emphasized, the volcanic area practically coincides 
with the hills and ridges just described and is surrounded on all sides b} r granitic 
rocks. 

Globe and Ironclad hills and Gold and Raven hills consist chiefly of heavy 
masses of breccia, and were scenes of great activity during the early }mars of the 
district. Near Poverty Gulch, just northeast of Cripple Creek, is the Abe Lincoln, 
not a large mine, but still actively worked with satisfactory results. Higher up are 


147 


148 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

the Gold King, with dividend records of $150,000, and the C. O. D., with a reported 
production of $600,000 and dividends of $150,000. Both were idle in 1904 and 
have attained their eighth or ninth levels. 

On the summit of Globe Hill are the Stratton properties of Plymouth Rock and 
Globe mines, in which extensive low-grade mineralization without many sharply 
defined veins seems to be the rule. Adjoining is the property of the Homestake 
Company, including the Ironclad mine, where direct cyaniding of oxidized surface 
ores is now carried on in a mill erected on the property. 

Gold Hill is crowned by the Anchoria-Leland mine, with a production of over 
$1,000,000 and dividends of $198,000. The shaft is 1,100 feet deep. The adjoining 
Moon-Anchor has paid dividends of $261,000, and the Half Moon (Matoa Gold 
Mining Company) has a gross production of $650,000 to its credit, but is reported 
to have paid only a small amount in dividends. None of these mines is being 
worked at present, except on a small scale by lessees. 

On the western slope is the Midget mine, actively worked at present, with a 
depth of 800 feet, a total production of $662,000, and dividends of $195,000. The 
Conundrum, in the same vicinity, is likewise worked with good results to a depth of 
600 feet. The Midget, like the mines described above, follows a vein in breccia, 
while the Conundrum is mining on a “basalt” dike in granite, close to the contact of 
the breccia. . 

In the deep gulch between Gold Hill and Raven Hill are situated the Anaconda, 
Doctor-Jackpot, and Mary McKinney mines, all working on sheeted zones forming 
lodes in the breccia. The Anaconda produced about $1,000,000, chiefly from 
upper levels, and is now being worked by lessees. The Mary McKinney is one of 
the most successful mines worked at present in the district. Its depth is 600 feet. 
The Doctor-Jackpot has $4,000,000 to its credit and likewise a handsome dividend 
record. The shaft is only 700 feet deep, water having until now prohibited deeper 
sinking. 

The breccia-granite contact is found on Guyot Hill a short distance south of 
the Mary McKinney. The extreme spur of Raven Hill, called Beacon Hill, is 
formed of an intrusion of phonolite in granite, and about this outlying volcanic 
center cluster a group of veins of great production and promise. On the eastern 
side of the hill are located the Prince Albert, Gold Dollar, and others, which are 
worked on a small scale by lessees. On the western side lie the El Paso, C. Iv. & N., 
and Old Gold mines, with their narrow but extremely rich fissure veins in granite, 
now actively and successfully worked. 

A great number of smaller mines have been worked on veins cutting the breccia 
of Raven Hill. The famous Elkton mine is situated in the deep hollow between 
Raven Hill and Battle Mountain. It has been working on an exceptionally long 
vein, partly contained in breccia, partly in granite, and generally following a 
“basalt” dike. The production approaches $6,000,000, and the depth attained is 
about 900 feet, excessive water having formed a serious obstacle to deeper sinking. 
Dividends amount to $1,200,000. The Moose mine, situated higher up on the slope 
of Raven Hill, had a good ore shoot, from which $500,000 was obtained. 

Continuing northwest, we soon attain the summit of Bull Hill, which affords a 
magnificent panorama, not only of the whole camp, but of a large part of the State 


u 

CD 

O 


o 

o 


o 

< 


o 
a: 


O 

> 

r> 

o 


-1 

HILL 

-1 

-J 

u_ 

Lk_ 



z 

I 

□ 

S 

X 

O 

Z 

o 

Ui 


(J 

UJ 


_J 


< 

> 


h- 

ID 

kJ 

< 

ZD 

H 

CD 

CQ 

ct 

CO 

< 

CD 


\~ 

£ 

< 

D 

O' 

</) 


11000 


10750 


10500 


10250 


10000 


11000 


10750 


10500 



SECTION ACROSS THE CRIPPLE CREEK DISTRICT FROM THE ABE LINCOLN MINE TO STRATTON’S INDEPENDENCE MINE, SHOWING BY SECTION AND PROJECTION THE RELATIVE VERTICAL POSITIONS OF THE PRINCIPAL SHAFTS, LOOKING NORTHEAST 

SHAFT AND TUNNEL. NAMES, CRIPPLE CREEK DISTRICT, WITH ELEVATIONS OF COLLARS AND PORTALS 


JULIUS BIEN&C0 UTH N.Y 


1 Mollie Kathleen .9,990* 7 

2 El Paso Gold King. .9,852 8 

3 Abe Lincoln....9,611 9 

4 Cripple Creek and 10 

Gold Hill tunnel....9,500 11 

5 C. 0. D.9,820 12 

6 Chicago tunnel.9,700* 


Hoosier.10,394 13 

Conundrum.9,680 14 

Gold Pass. 10.080* 15 

Moon Anchor.9,865 16 

Midget.9,796 17 

Good Will tunnel.. ,9.467 18 


Anchoria Leland. 


Ophelia tunnel.. 


Plymouth Rock 


10,139 

19 

Mint... 

..9,804 

25 

W. P. H. 

10,305* 

31 

Peggy . 

. .9,567 

37 

Gleason. 

. 10,653 

43 

Kalamazoo. 

10,620* 

10,155* 

20 

Pointer. 

..9,642 

26 

Jerry Johnson... 

.10,330* 

32 

Mary McKinney.. 

..9,533 

38 

Old Gold. 

.9,230 

44 

Ingham. 

10,241 

.9,268 

21 

Ironclad ..... 

.10,400 

27 

Anaconda tunnel. 

. .9,493 

33 

Dolly Varden. 

..9.795 

39 

Sheriff. 

. 10.435* 

45 

Standard tunnel . 

.9,027 

10,405* 

22 

Sunshine. 

.10,180 

28 

Damon. 

.10,333 

34 

Morning Glory... 

..9,721 

40 

Doctor. 

. 10.010* 

46 

El Paso, new shaft 

.9,358 

10,185* 

23 

E. Porter Gold 


29 

Howard. 

. .9,605* 

35 

Jackpot. 

. .9,770* 

41 

Wild Horse. 

. 10,653 

47 

Pinnacle. 

10,260* 

10,435* 

24 

King .. .. 

Caledonia. 

.10,080* 

. .9,410* 

30 

Londonderry. 

. 10,551 

36 

Katinka .. 

. .9,300 

42 

C. K. & N. 

..9,300 

48 

Jennie Sample... 

10,043 


49 Ophir.9,845 

50 El Paso drainage 

tunnel.8,783 

51 E! Paso, old shaft .. .9,370 

52 Gregory.10,287 

53 Ida May, new shaft. 10,370* 

54 Ida May, old shaft. 10,365* 


55 


. 10,380* 

61 




67 


. .9,493 

74 


56 

Joe Dandy. 

. 10,376 

62 

Burns 



68 

American Eagle. 

. 10,750 

75 

Gold Sovereign, 

57 

Empire State, Or- 


63 

Newell tunnel.. 

. . .8,930 

69 

Zoe. 



Jackson shaft ... 


phan shaft. 

. 10,520 

64 

Buena V 

Ista.... 

...10,440 

70 

Prince Albert.... 

..9,580* 

76 

Shurtloff No.2.... 

58 

Pharmacist. 

.10,630 

65 

Block 8 


.. 10,080* 

71 

Logan . 

..10,472 

77 

Gold Sovereign, 

59 


.10,555* 

66 

Pinto 



72 

Gold Dollar. 

.. 9,509 


Whisper shaft .... 

60 

Tornado. 

.10,114 





73 

Elkton . 

.9,734 

78 

Free Coinage, Mer 












cer shaft. 


.10.527 


10,330 


79 Free Coinage, Mur- 85 

phy shaft .10,600* 86 

80 Dante.10,355* 87 

81 Moose.10,117 88 

82 Orpha May.10,538 89 

83 Deadwood No. 1.. 10,545 90 

34 Thompson.9,755 


Trilby.10,255* 91 

Smuggler .10,521 92 

Trachyte. 10,462 93 

Lucky Guss No. 1.10,510* 94 

Findley.10,399 95 

Blue Bird.10,397 96 


Lucky Guss No. 2.. 10,420* 97 

Delmonico .10,445* 98 

Deadwood No. 2 .10,410* 99 

Dexter.10,285* 100 

Hull City.10,279 101 

Eclipse.9,689 102 


Victor.10,540 103 

Los Angeles.10,320* 104 

Rubie .10,325* 105 

Carbonate Queen . .9,911 106 

Colorado City.10,285* 107 

Vindicator No. 2.. 10,186 108 


Last Dollar.10,278 

May B.9,813 

Portland No. 3 .. . . 10,332 

Coriolanus.10,237 

Vindicator No. 1... 10,209 
Modoc No. 2.10,150* 


109 

Lillie. 

.... 10,222 

115 

Portland No. 2.. 

.. 10,244 

122 

110 

Clyde. 

.... 10,085 

116 

Golden Cycle... . 

. . 10.066 

123 

111 

Christmas.,... 

. ..10,161 

117 

Portland No. 1. . 

.. 10,082 

124 

112 

Ajax. 

.... 10,108 

118 

Theresa. 


125 

113 

Santa Rita.. . . 

.9,634 

119 

Monument. 

.. 10,000“ 

126 

114 

Granite. 

.10,140 

120 

121 

Dead Pine. 

Dillon. 

. 9,915* 

127 

128 


Stratton's Ind. No.2.9,960* 

Gold Coin.. ..9,765 

MaryCashen. 9,764 

Gold Knob.9,990* 

Strong.9,756 

Stratton’s Ind. No. 1.9,844 
St. Patrick.9,615 


* ELEVATION 


APPROXIMATE 
























































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































PRELIMINARY REVIEW OF THE MINING INDUSTRY. 


149 


of Colorado. Toward the east, and 5,000 feet lower, spread the great plains at the 
foot of the Rocky Mountains; westward the Sangre de Cristo, Collegiate, and Mos¬ 
quito ranges—a snowy and jagged line of ramparts—define the distant horizon. 

A multitude of small mines occupy the southwestern slope of Bull Hill. On 
the northwestern side an area of breceiated granite appears among the volcanic 
rocks, and in this formation is situated the Wild Ilorse mine. This lode, which has 
been worked to a depth of 1,250 feet, has produced over $1,000,000, but is now 
operated only by lessees. A number of smaller producers may be found on the north¬ 
ern slope, toward Cameron, among them the Damon, Jerry Johnson, W. P. Id., and 
Pinnacle. 

Those who have followed this description on a map will have noticed that the 
mines are chiefly situated on the periphery of a circular area, the central part of 
which, comprising the upper part of Squaw Gulch, has thus far yielded very little. 
Few strong veins have been met with in this part of the breccia, but, on the other 
hand, the developments in depth are not extensive. 

On the east and southeast sides of Bull Hill begins that most important belt of 
lodes which extends southward to Victor and includes the richest group of producers 
in the camp. A characteristic feature of this belt is the intrusion into the breccia 
of thick masses of latite-phonolite and syenitic rocks. 

With few exceptions the veins of this belt strike north-northwest. We may 
begin the description with the system of linked veins, 3,000 feet long, covered by the 
Isabella and Victor mines. The last-named mine, on the southern end of the system, 
is situated just below the western slope of Bull Cliff. It has been worked to a depth 
of over 1,000 feet, has produced about $2,200,000, and has paid dividends amounting 
to $1,150,000. The Isabella has attained a depth of 1,127 feet, produced $3,200,000, 
and paid dividends of $600,000. Both mines lost their pay shoot in depth, but are 
still worked by lessees. 

The small but rich cross veins of the Empire State, Burns, Pharmacist, and 
Zenobia connect this vein system with that of the Stratton mines on Bull Hill. 
South of the Burns begins the great Vindicator vein system, traced southeastward 
for a mile through the Findley, Hull City, Vindicator, Lillie, and Golden Cycle mines. 
The Hull City and the Lillie have each produced over $1,000,000, the Vindicator 
and Golden Cycle over $2,000,000 each, all with corresponding dividend records. 
The Lillie is deepest, having attained 1,500 feet. Next in depth is the Vindicator, 
1,200 feet. All of them, except the Lillie, are still actively worked. In the whole 
system water has been and still is a source of trouble. The deepest mine evidently 
drains all the others in this vicinity. 

The Stratton properties on Bull Hill, with the Logan, Orpha May, and Pikes 
Peak veins, on which maximum depths of 1,200 and 1,500 feet have been attained, 
are now worked only to a slight extent, whereas in the early days of the camp they 
were highly productive. 

This vein system is continued southward in the Last Dollar mine, now working 
at a depth of 1,270 feet. The production exceeds $1,000,000. South of the Last 
Dollar the veins enter the Modoc ground, a mine worked for a long time with gratify¬ 
ing success. The Blue Bird, an old-time producer, is situated a short distance west 
of the Last Dollar. 


150 GEOLOG'? AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

South of the Modoc is the Battle Mountain vein system, crossing from the 
granite into the breccia, with general northerly or north-northwesterly directions, 
and distinguished by heavy production and ore bodies of imposing size. None of 
the veins is of great length, and the whole system extends scarcely a mile along the 
strike of the veins. The veins can not be directly connected with others already 
described, though, in its general trend, the system heads toward the Dexter, Blue 
Bird, and Moose veins. 

Beginning on the southwestern side, we first come to the Gold Coin mine, the 
veins of which are in granite; one of them is successfully worked at present at a depth 
of 1,200 feet. The total production approaches $6,000,000; the dividends paid 
exceed $1,000,000. North of the Gold Coin is the Ajax, working partly in the 
veins, partly in large, irregular ore bodies in the granite. The total production 
is very considerable. The depth attained is 1,200 feet. 

Between this and the Portland vein system, almost within the town of Victor, 
are the Granite, Dillon, and Dead Pine veins. They are worked at present at 
depths of 800 to 1,000 feet. 

The Portland vein system begins on the south at the Strong mine, now worked 
at a maximum depth of 900 feet, on a vein in granite that follows a “basalt” dike, 
which is in places accompanied by a phonolite dike. The mine is an unusually reg¬ 
ular and profitable producer, the total dividends since 1892 amounting to $2,500,000. 

The veins of Stratton’s Independence run about parallel to those of the Strong, 
a few hundred feet eastward. They extend from the granite into the breccia, fol¬ 
lowing for some distance a phonolite dike. The production of this mine amounts 
to over $11,000,000, with a dividend record of $4,000,000 since 1899. At present 
the company is leasing the various levels to tributers. From the two properties 
last described the vein systems continue into the Portland mine, but in the northern 
part of that great property are replaced by another and still richer aggregate of veins, 
the Captain system. The Portland is, beyond question, the most prominent mine 
of the Cripple Creek district. Its total production from 1894 to the end of 1903 
amounted to $18,000,000, derived from 466,000 tons of ore (both in round figures), 
from which $4,600,000 has been paid in dividends, the remainder going to acquire¬ 
ment of territory, extensive milling and mining plants, and operating expenses. 

Outside mining properties .—The area outside of the principal volcanic area con¬ 
tains very few productive properties, but it is by no means barren. A great deal 
of money has been spent here, usually with unsatisfactory results. Although there 
are many properties of merit and although much honest effort has been made in this 
part of the district, it has long been the favorite camping ground of concerns more 
or less lacking in stability. 

The granite hills west and south of the city of Cripple Creek contain few pros¬ 
pects; phonolite dikes occur in places, but usually show little value. Along Gold 
Run and Arequa Gulch prospects with a little ore have been found, down to the junc¬ 
tion with Cripple Creek, and even at isolated places below this locality. Grouse 
Hill, with its phonolite cap, shows many prospects from which occasional good 
assays have been obtained, but neither here nor on Straub and Brind mountains 
has anything of permanent value been developed thus far. It is claimed that ore 
bodies of low grade, containing a few dollars per ton, exist. 


151 


PRELIMINARY REVIEW OF THE MINING INDUSTRY. 

I 

The breccia caps of Mineral, Carbonate, and Tenderfoot hills are dotted with 
prospect dumps and even shafts several hundred feet deep. Nothing of permanent 
value is recorded from Mineral Hill, though fairly productive placers have been 
worked at its southwestern base, almost in the town of Cripple Creek. 

On Carbonate Hill the Elkliorn has been a small producer; on Tenderfoot Hill 
the Friday, Hoosier, Black Diamond, and Mollie Kathleen contribute to the produc¬ 
tion. Two miles north-northwest of Cripple Creek is the Galena mine, the vein of 
which follows, for a part of its course, a phonolite dike in granite and has a small out¬ 
put to its credit. About the same distance north of the city is the small volcanic 
center of Copper and Rhyolite mountains. At the former the Fluorine mine has 
produced $160,000, and low-grade ore is now being cyanided. Prospects are found 
on Rhyolite Mountain, and in fact all over the flat, granite country between it and 
Trachyte Mountain. The Lincoln mine, near Gillett, and several other prospects 
farther south, along a belt of phonolite dikes, have produced a little ore. It is 
claimed that there are low-grade veins on both sides of Bernard Creek, northwest of 
Gillett , in a region of granite with occasional dikes and masses of phonolite. Trachyte 
Mountain, southeast of Gillett, is covered by phonolite, and a little ore is occasionally 
found in veins at its southern foot. Some work has also been done on Cow Mountain, 
about 4 miles northeast of Bull Hill. 

The eastern margin of the central volcanic area, east of Victor Pass and 
extending southward across Big Bull Mountain to Brind Mountain, has thus far failed 
to produce anything of importance, though well covered by prospects. A survey 
of these outlying parts of the district serves to emphasize strongly the remarkable 
concentration of deposits within the narrow limits of the central volcanic area. 

EXTEXT OF UNDERGROUND DEVELOPMENT. 

At the time of the earlier survey the deepest shafts, those of the Moose, Phar¬ 
macist, and Anna Lee mines, were down only about 400 feet, while few of the other 
mines were over 200 feet in depth. Many subsequently prominent mines were then 
mere prospects or had not been located. 

The deepest shaft at present is the Lillie, which is over 1,500 feet deep, although 
the Stratton’s Independence shaft, 1,400 feet deep, has the lowest sump in the 
district. The American Eagle shaft is nearly as deep as the Lillie, while there are 
about 20 other shafts over 1,000 feet in depth, and at least 100 shafts deeper than the 
deepest workings existing in 1894. As regards absolute elevations, the Gold Hill 
shafts are down to a level of scarcely 9,000 feet above sea; the Elkton, El Paso, and 
Lillie shafts descend to 8,750 feet; Stratton’s Independence reaches the lowest level 
at 8,450 feet; while the Gold Coin shaft, at 8,550 feet, is of interest from the fact 
that the deepest ore shoot in the district is now being stoped from its twelfth level. 

The amount of drifting and cross cutting accomplished since the earlier survey 
is more than commensurate with the increased number and depth of the shafts, and 
the district is further intersected in various directions and at different levels by 
two long tunnels run for drainage purposes and by a dqzen or more extensive adits, 
many of which have their portals in the granitic rocks and extend well into the 
central part of the breccia area. 


152 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

PLACERS. 

Owing to the light, powdery, or spongy form of the gold set free by the oxidation 
of the tellurides, placer deposits have been formed only to a very subordinate extent. 
Penrose states that limited areas of placer ground have been worked at Hull City, 
along Beaver Creek, in Squaw Gulch, Arequa Gulch, and on Wilson Creek. The 
principal placers were found in the northern part of the town of Cripple Creek, on 
the southerly slopes of Mineral and Carbonate hills, particularly in the broad hollow 
on the southwest side of Mineral Hill. A fair amount of gold was taken out from 
this shallow ground in the early days by sluice, rocker, or dry washer; in many 
cases the pay dirt was extracted b} r drifting from little pits or shaits. A certain 
amount of payable ground is said to remain here, and, were water available, a con¬ 
siderable area could probably be washed with profit. The gold appears to have been 
derived from veins in the breccia directly southwest of the summit of Mineral Hill , 
extensive prospecting has, however, thus far failed to reveal any primary deposits 
of value. 


CHAPTER VII-STRUCTURE OF THE GOLD DEPOSITS. 

PRINCIPAL TYPES OF DEPOSITS. 

With few exceptions the ore bodies, of whatever shape, are causally connected 
with fissures. The 'most important types of auriferous ore bodies occurring in the 
district are: 

(1) Tabular in form and strictly following simple fissures or sheeted zones. A 
subtype comprises lodes in which the sheeted zone follows “basalt” or phonolite 
dikes. 

(2) Irregular bodies adjacent to fissures and formed by replacement and 
recrystallization of the country rock, usually granite. 

These types are not always sharply distinct, but may be connected by deposits 
of intermediate character. 

All the ore bodies, of whatever type, exhibit certain common features which 
serve to distinguish the deposits of Cripple Creek from those of most other mining 
districts. In the first place, the actual openings in the rocks available for the depo¬ 
sition of ore are, as a rule, remarkably narrow. In the second place, the amount of 
material carried in the mineralizing solutions and deposited as gangue and ore 
minerals was comparatively small. In consequence of these two conditions, the 
district contains no such massive veins, solidly filled with quartz or other vein 
minerals, as are characteristic of the San Juan region in Colorado or the Mother Lode 
region in California. Even the small fissures of the Cripple Creek district are 
seldom completely filled, but have a characteristic open or vuggy structure. Where 
the fractures are unusually wide, or where the rocks are extensively shattered, as in 
the Midget and Moose mines, the small volume of available vein matter is particularly 
noticeable. The walls of such fractures and the fragments of the shattered rock are 
often merely coated with a thin deposit of quartz, fluorite, and other minerals. As 
the rich telluridps were usually among the minerals last to form, and are particularly 
abundant on the walls of the vugs, it is probable that had quartz, fluorite, or other 
gangue minerals been more abundantly deposited, the ores would have been of much 
lower grade. 

LODE FISSURES. 

DISTRIBUTION. 

As elements of geological structure, the lode fissures of Cripple Creek are 
exceedingly inconspicuous. They are marked neither by bold outcrops of quartz 
nor by superficial bands of ferruginous gossan. They seldom fault perceptibly the 
structures which they traverse and they are not sufficiently different from the mass 
of the rocks, as regards resistance to erosion, to have perceptibly influenced the 
topographic development of the district. It is this obscurity that, as already 


153 


154 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

related, retarded the discovery of the ore deposits, and that to-day renders it impos¬ 
sible to follow the veins over the surface without first stripping off the*soil and loose 
rock or sinking test pits. In the early stages of mining development in the district 
the course of a newly discovered lode was rarely known until underground work had 
well advanced, and consequently few of the claims were laid out along what after¬ 
wards proved to be lines of outcrop. Furthermore, many of the lodes, such as the 
“Captain system” of the Portland mine and the Dorothy vein of the Gold Coin mine, 
apparently do not reach the surface. Under these circumstances, discussion of the 
lode fissures is limited to those whose positions and courses have been determined 
by underground work. 

In a hilly region the lines of outcrop of inclined veins, when plotted on a map, 
are complicated by curvature due to the irregularity of the topographic surface 
In a study of the fissure systems of a district such as that of Cripple Creek, it is 
desirable to eliminate this unessential complexity and to consider the traces of the 
fissures upon one or more horizontal planes. In PI. XII the principal lodes of the 
district are represented with the courses and relative positions that they would 
have if they outcropped on a level plain 9,500 feet above the sea. A few veins, 
known only at considerable distances above or below the 9,500-foot plane, are 
represented by dotted lines, and have the elevation at which they are known nearest 
to 9,500 feet indicated in figures. The diagram shows also the outlines of the main 
volcanic neck and of the Beacon Hill phonolite plug at the surface, data being 
insufficient for fully delineating these features upon the 9,500-foot plane. 

As shown in PI. XII, the productive fissures are most strongly and abundantly 
developed in the volcanic neck. They are not confined to the neck, however, for 
there is a very important group near Victor, partly in granite and partly in the 
volcanic rocks, and there is a prominent group in the granite of Beacon Hill. Pro¬ 
ductive fissures occur also at other points in the granites and gneiss of the pre- 
volcanic plateau. But even when all outlying fissures are considered, the grouping 
of the lodes within a small area, which is that of the volcanic neck plus a sector of 
a narrow concentric zone of the granitic rim, is the most striking fact of distribution 
brought out by the diagram. Within this general group the fissures of Beacon 
Hill constitute a subgroup clustered about the phonolite plug which forms the core 
of the hill. 

Within the volcanic neck the fissures are most abundant and persistent in its 
southern half. They are crowded within the V-shaped or crescentic area wherein, 
as previously shown, the breccia extends to great depth and most clearly fills a part 
of the old volcanic throat. In the very center of the generally productive tract and 
roughly bounded by lines connecting the summits of Globe, Ironclad, Bull, Raven, 
and Gold hills is an area within which few important productive fissures are known. 
This relatively barren ground includes the superficially isolated granite mass of Bull 
and Ironclad hills and the schist mass of Fairview. North of this area, extending 
to Tenderfoot and Carbonate hills, is a part of the district which, while moderately 
productive, exhibits far less Assuring than does the portion stretching from Anaconda 
to Victor and from Victor to Altman. 

It is certain that the district contains many important fissures not shown in 
PI. XII, but that plate probably expresses fairly well the essential facts of lode 


U.S. GEOLOGICAL SURVEY 


PROFESSIONAL PAPER N0.54 PL. XII 



Hoosfer 


PLAN OF THE PRINCIPAL FISSURES 

OF THE 

CRIPPLE CHEEK DISTRICT 

COLORADO 

SHOWN AS INTERSECTING A PLANE 9,500 FEET ABOVE SEA LEVEL 

The geological boundaries are projected 
vertically from the surface upon this plane 

Bv Waldemar liindsren and F L. Kansome 


Scale 

500 lOOO 


2500 feel 


1905 


The volcanic neck 


Phonolite dikes 


, , -, 

The Beacon Hill phonolite plug mmmm , 


Basic dikes 


Granite, gneiss, and schists & Lodes 






JULIUS BIENfc CO LITH N Y 



















































































STRUCTURE OF THE GOLD DEPOSITS. 


155 


distribution. That, the Assuring is in fact local and does not extend indefinitely 

and with undiminished intensity into the surrounding rocks of the prevolcanic 

plateau is indicated not only by the results of mining development as plotted in PI. 

XII, but by the behavior of underground water and by the distribution of basic 

dikes, as will subsequently be shown. 

* 

DIRECTION OF FISSURING. 

The major fissures, as appears in PI. XII, have a recognizable though irregular 
radial plan. In the western and southwestern parts of the district the prevailing 
strike is northeasterly; in the southern part it is northerly; and in the southeastern 
and eastern parts of the productive area a northwesterly strike predominates. 
There is much irregularity, and there are some fissures in all parts of the field that 
do not conform to this plan. When, however, account is taken of the heterogeneous 
character of the material filling the volcanic neck and the many dikes and irregular 
intrusive masses tending to deflect fissures from courses that they might follow in a 
homogeneous medium, it is less surprising that individual fissures should be eccentric 
than that the Assuring should on the whole so clearly exhibit a definite arrangement. 

While the general disposition of the fissures is radial, they converge rather to 
various parts of a central tract than to a single point. This tract is that already 
referred to as containing relatively few important fissures and as corresponding 
approximately with the drainage basin of Squaw Gulch above Anaconda. It 
includes the island-like mass of granite of Bull and Ironclad hills and the similar 
schist mass of Fairview. North of this tract lies a mass of breccia extending to 
Tenderfoot and Carbonate hills, in which the rather scanty known fissures suggest 
little systematic arrangement. The general radial plan thus prevails over a sector 
comprising about 270° of the rudely circular productive area. 

The radial arrangement of the lode fissures is shared to a certain extent by the 
dikes, particularly by the “basalt” dikes. It would thus seem that whatever the 
nature of the stresses which produced the lode fissures, similar stresses must have 
formed the fissures followed by the basic dikes. The ore deposition and some of the 
Assuring were later than the dike intrusions, but it is not certain that the fissures 
themselves can be separated into an earlier and a later group—that filled with 
“basalt,” this with ore. It is probable that the basic magma was injected into 
a part of the earlier fissures, the remainder being left empty and in part subse¬ 
quently filled with ore. 

The Cripple Creek lodes, as will be shown later, have a sheeted structure. As 
sheeting is a characteristic result of compressive stress and as the fissures produced 
by a generally simple stress, like the compression of a block of glass in a vice, tend 
to form two intersecting groups of parallel conjugate fissures, the occurrence of a 
radial system rather than of two or more conjugate systems is noteworthy. The 
latter feature is common to many districts, even where the lodes are not regular 
sheeted zones and are therefore not so clearly due to compression. A general radial 
grouping of the fissures over a whole mining district is comparatively rare, and 
where associated with well-defined sheeting indicates the operation of compressive 
stresses of rather unusual character. 


156 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

Besides the dominant radial arrangement, it should be noted that northwest 
and northeast veins are present together in various parts of the district, as in the 
Isabella, Molly Kathleen, and Abe Lincoln mines. The presence of both sets of 
fissures is particularly marked in the Isabella mine, in the northeastern part of the 
district, where the northeast or “cross” veins have a local radial grouping with 
northeastern convergence (fig. 44, p. 3S8). This development of intersecting sheeted 
zones is indicative of compressive stress, especially as on the whole the two systems 
seem to have formed simultaneously and do not as a ride fault each other, though 
there may be some offsets, as in the case of the Klondike and Isabella veins. 

There are many other examples of local groups of divergent fissures besides 
that of the Isabella cross veins. Thus the principal fissures of the Victor, Vindi¬ 
cator, and Golden Cycle mines show a tendency to branch or diverge toward the 
northwest. The principal lodes of Stratton’s Independence mine, on the other hand, 
diverge toward the southeast, and those of the Gold Coin to the south. 

DIPS. 

Most of tlie fissures are steeply inclined, the average dip being about 75°. 
Many are practically vertical and dips lower than 50° are rare. Fairly regular 
dips down to 1,200 feet in depth are shown by the Lillie (vertical), the Buena Vista 
(60°), Pharmacist (60°), and the Findley (85°) lodes (figs. 50 and 52, pp. 414, 420). 
There are, however, a few fissures which lie at unusually low angles, notably 
those of the Howard flat vein in the Mary McKinney and Anaconda mines, of “the 
flat vein” in Stratton’s Independence mine, and several unnamed fissures in the 
Damon and War Eagle mines. The average dip of these flat veins is probably 
about 20°. Some of those in the Damon are nearly horizontal, but others dip at 
45°. There is thus no sharp distinction, as regards dip, between the so-called flat 
veins and the nearly vertical lodes. 

While in any local group the fissures dipping in one direction usually greatly 
predominate over those dipping in the other, yet adjacent lodes seldom all dip in 
the same direction. No systematic relation has been found between the dips, on 
the one hand, and the distribution of the fissures or the general structure of the 
district, on the other. 

PERSISTENCE. 

In a district like Cripple Creek, where knowledge of the lodes is derived almost 
exclusively from underground work and where the lodes themselves are often ill 
defined, discussion of the persistence of the fissures can not entirely escape a vague¬ 
ness inherent in the subject. Miners are concerned with a fissure only so far as it 
carries, or seems likely to carry, ore. Although exploration in some cases has been 
pushed to the point where a fissure or fissure zone can no longer be distinguished 
from the irregular jointing present in nearly all rocks, in other cases the search for 
ore has been abandoned while the fissure could still be readily followed and while 
its length or depth remained undetermined. Few fissures have been explored so 
carefully that their extent in the directions of strike and dip is known. 

In the Cripple Creek district individual fissures, or fissure zones of such regu¬ 
larity and narrowness that they may be classed as lodes, are rarely known to exceed 


STRUCTURE OF THE GOLD DEPOSIT*. 


157 


half a mile in length. Lodes of approximately this length are the Mary McKinney, 
Doctor-Jackpot, and Buena Vista. Some of the broader zones of nearly parallel, 
linked, or imbricated fissures are, however, traceable for over a mile. 

Many of the most productive fissure zones are remarkably short. The so-called 
Captain system in the Portland min#, for example, in which the fissures, while 
collectively rich, are at best individually small and inconspicuous, contains few 
lodes that can be traced for over 300 feet. Cross cuts have more than once passed 
within a few feet of ore bodies 50 or more feet in width which were discovered only 
by subsequent exploration. In such broad zones of individually nonpersistent 
fissures there is often great difficulty in identifying veins crosscut at levels 100 feet 
apart, without actually stoping them. This is especially the case in the Portland, 
Stratton’s Independence, and Vindicator mines. The productive veins in the 
granite of the Ajax mine, southwest of the shaft, are probably all less than 500 feet 
in length. In the Anchoria-Leland mine some fissure zones which are very regular 
for short distances dwindle in a few hundred feet to a single indistinct crack or come 
to an end at the junction with another fissure zone of different strike and dip. In 
the Last Dollar mine the main system of parallel fissures is crossed by east-west 
cross veins which can be followed only for short distances. 

Information concerning the persistence of fissures in depth is even less satis¬ 
factory than that relating to length, as in many cases it is impossible to discriminate 
clearly between depth of pay shoots and depth of Assuring. The ore and the fissure 
zone are not necessarily coextensive, though often little is known of the extension 
of the fissures below the bottom of an ore shoot. 

In general the persistence of a fissure down the dip seems to be roughly pro¬ 
portional to the length of the fissure. The long fissures, such as those of the Elkton 
and Mary McKinney lodes, can probably be followed far below the present bottoms 
of the mines. Many of the shorter fissures, however, are known to die out at 
moderate depth and are often succeeded by overlapping parallel fissures of similar 
character. 

These relations are well illustrated in the Portland mine. The No. 1 Hidden 
Treasure vein was first recognized on the 350-foot level and was productive down 
to level 9. If the fissure zone continues to level 10, it is very inconspicuous. The 
No. 2 Hidden Treasure has been productive from level 6 to level 8. The No. 3 
Hidden Treasure is not known above level 6, although at the bottom of the mine 
it is the only lode of the group which was known at the time of visit. The short 
lodes of the Captain group are of little importance above the 220-foot level, attain 
their maximum development near the 350-foot and 500-foot levels, and become 
very indistinct on level 7, although there are still traces of this group of fissures on 
level 10. Within the group individual fissures, or narrow zones of fissures, die out 
and overlap as do the Hidden Treasure lodes. The No. 4 Lee, on the other hand, 
though not a long lode, is unusually persistent in depth, being known on practically 
all the levels of the Portland mine. The Diamond vein, a fissure zone in granite in 
the same mine, is not known above level 5. Its fissures are unproductive, though 
distinct, on level 10. The Portland vein becomes very indistinct below level 6 
and on the lower levels is unknown. 


13001—No. 54—0& 


12 



158 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

Ill Stratton’s Independence mine the Emerson and Grant lodes apparently 
die out near level 5, being unknown at lower levels. The No. 6 vein, on the other 
hand, is not known above level 5. In the Ajax mine the zone of Assuring known 
as the Apex vein is known only above level 4. In the Gold Coin mine the Dorothy 
lode first appears near level 8 and continues to the bottom of the mine. On the 
1,200-foot level of the Vindicator mine the strong No. 1 vein, known all the way 
from the surface to the 1,000-foot level, does not appear. Nonpersistence of lodes 
is shown also in the Molly Kathleen mine, where the fissures on the 700-foot level do 
not correspond to those on the 200-foot level, and in the Abe Lincoln mine. The 
Buena Vista lode remains well defined on the 1,200-foot level, but has been followed 
northeast on that level to a point where it becomes very indistinct. Fissures not 
known at the surface have been found in the lower levels of the Gold Coin and Hull 
City mines. 

Other illustrations of the fact that the lode fissures do not all begin at the sur¬ 
face and extend indefinitely downward, but that many of them are at least as well 
defined as regards their upper or lower limits as they are along their lines of strike, 
may be found in the detailed descriptions of mines in the latter part of this report. 

In some places the fissures are very irregular, the ore occurring in stockworks 
made up of many short veins and seams belonging to several fissure systems. Such 
are some of the deposits in the Anaconda mine near the Mary McKinney line, in 
the gneiss of the Midget mine, in the Sheriff, Homestake, and New Haven mines, 
and in the Stratton properties on Globe Hill. Many short veins in one small mine 
are shown in the Dante (fig. 42, p. 371) and also in the Monument and Dillon mines 
(PI. V, p. 26). 

The question whether the fissures are as large and as abundant at greater depth 
as they are near the surface is a very important one as regards the economic future 
of the district. Unfortunately it is a question which, considered independently of 
the vertical distribution of ore bodies, requires for its satisfactory answer more 
complete data than are at present obtainable. That some fissures practically die out 
below is certain; but it is equally true that others, which are not known at the sur¬ 
face, appear in the deeper workings of the mines. As the extent of a productive 
fissure is generally less definitely determined than the extent of its contained ore 
bodies, the decision whether with increasing depth of workings more fissures appear 
than disappear, or vice versa, is not easily reached. 

Detailed examination of practically all the accessible mines in the Cripple 
Creek district has, however, led to the conclusion that the fissures do, in general, 
become less abundant and less conspicuous as greater depth is attained. No mine 
exhibits this feature better than Stratton’s Independence, in which the very com¬ 
plex systems of productive fissures on the fifth and higher levels contrast most strik¬ 
ingly with the few insignificant and unproductive fractures visible on level 14. In 
a less degree the same feature is shown in many others of the deep mines. It should 
be clearly understood, however, that tins statement applies to the Assuring con¬ 
sidered as a whole, and is made with the knowledge that some fissures appear in depth 
which are not visible near the surface and that therefore some fissures, so far as 
experience goes, increase in size downward. 


STRUCTURE OF THE GOLD DEPOSITS. 


159 


INFLUENCE OF COUNTRY ROCK. 

Fissures are most abundant in the breccia and in the Pikes Peak granite adja¬ 
cent to the volcanic neck. Productive lodes occur, however, in all the other rocks 
within or near the neck, with the possible exception of the schist. The latite- 
plionolite, on the whole, seems less favorable than breccia to the development of 
ore-bearing fissures. Many fissures in breccia, such as the Captain veins of the 
Portland mine, terminate at or near the contact with masses of latite-phonolite, 
though others, like the Pharmacist, the Isabella system, and the Vindicator system, 
pass from breccia into latite-phonolite without noticeable change. 

Owing to their tendency to develop a platy parting parallel to their walls, 
dikes of phonolite or “basalt” when they happen to lie in the general direction of 
Assuring, frequently become sheeted zones. As examples of such occurrences may be 
mentioned parts of the Independence vein, the Portland vein, the Montana vein 
of the Gold Coin mine, the Apex vein of the Ajax mine, and the Cobb vein of the 
Moon-Anchor mine. In the lower levels of the Hull City mine one of the veins 
follows a dike of latite-phonolite, 10 feet wide, in breccia. This is the only instance 
observed in which a dike of this rock contained ore. 

When, however, a dike lies across the planes of Assuring, the Assures may con¬ 
tinue through the phonolite, but more often they become indistinct or irregular in 
that rock, as will be described when an account is given of the detailed structural 
features of the Assures. 

The general behavior of a Assure zone at a contact between two rocks depends 
largely upon the angle at which the plane of the lode meets the plane of the contact. 
If the two are nearly perpendicular the Assures may stop at the contact or they 
may cut through it without deAection. Instances of a Assure zone ending abruptly 
at a contact between two rocks are not common in the district, though there is often 
a marked change in the character of the ore at such points. The Diamond vein of 
the Portland mine, which is in granite, ends against the breccia, but the original 
relation has been obscured by slight faulting along the contact. The Gold Coin- 
Dead Pine Assure zone in granite has been followed to the contact with the breccia, 
where it apparently terminates. The No. 6 vein of Stratton’s Independence mine 
is known only in the granite, and the Emerson vein of the same mine is known only 
in the breccia. It could not be determined, however, at the time of visit, whether 
these Assures actually end at the contact. The Independence and Bobtail veins, 
on the other hand, pass from granite to breccia without deAection, though the 
Independence, like the No. 2 vein of the Portland mine, coincides with a portion 
of the contact that happens to lie in its course. The C. K. & N. Assure zone, which is 
regular and persistent in the granite, ends on the west against the phonolite sill of 
the Old Gold mine. 

When a Assure zone and contact meet at an acute angle the Assures may change 
their course and follow the contact, particularly if it is the wall of a dike, as in the 
case of the C. Iv. & N. vein and the El Paso phonolite dike, described on pages 
351-352, 356. In some instances, such as that of the El Paso vein (Ag. 39, p. 350), 
the deAection is only partial, the Assures Anally crossing the dike and continuing 
pn the other side with their original course. 


160 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


It is rather remarkable that the contact between the breccia and the sur¬ 
rounding granite is so rarely the seat of ore deposition, though some of the most 
important ore bodies in the district are found in its immediate vicinity. The contact 
itself seems to contain ore only where, as in the case of the Independence vein and the 
No. 2 vein of the Portland mine, it is locally coincident with a zone of Assuring 
which is productive also at other points. A possible exception to this last statement 
is the Contact vein in the W. P. H. and Damon mines, which follows the contact 
between schist and breccia for at least 300 feet in depth, dipping steeply southwest. 
It is ore bearing in places. 

The Wild Horse vein, with its long curved course, deserves special mention. 
Near the surface it follows approximately the contact between the granite and the 
breccia, but in depth it passes entirely into the granite. The dip is irregular, being 
in some places vertical and in others to the west at a high angle. 

STRUCTURAL FEATURES. 


The structure associated with the deposits most characteristic of the district 
is that known as a sheeted zone. As here developed, such zones consist of a vary¬ 
ing number of narrow, approximately parallel fissures which 
collectivelv form a lode ranging from a few inches to 50 or 60 
feet, or rarely 100 feet, in width. Within such uncommonly 
wide belts of fracture, however, can usually be distinguished 
two or more zones of concentrated Assuring which lie close 
enough together to be mined as a whole. In other words 
the very wide belts are compound 
sheeted zones, of which the most con- 



Rich ore 


Fig. 4.—Structure of La Bella 
vein, Golden Cycle mine, 
level 9. Rock is very fresh 
latite-phonolite. Central 
seam carries visible calaver- 
ite. Screenings across whole 
width assay 2 ounces per ton. 


Captain veins in the Portland mine. 
Usually the sheeted zones are from 2 
to 10 feet in width. 

As a rule the fissures are mere cracks, 
showing no brecciation, slickensiding, 
or other evidence of tangential move¬ 
ment of the walls. There are some 
notable exceptions to this statement, as will presently be 
seen, and appreciable displacement has occurred along some 
of the veins. But the movement of one wall past the other 
has probably in few instances exceeded 1 or 2 feet. 

A sheeted zone on a small scale is well shown by PI. XIII, 
from specimens from the mineralized basic dike of the Conun¬ 
drum mine. In this case the fissures are filled with fluorite. 

Very often, however, a single narrow fissure is accom¬ 
panied by irregular fracturing of the adjacent rock. Such a 
structure, which is not properly a sheeted zone, is illustrated 
in fig. 4, a sketch of the La Bella vein on level 9 of the Golden 
Cycle mine. The country rock in this case is latite-phonolite. 



Scale 

5 


10 ft. 

_I 


Fig. 5.—Legal tender vein. 
Golden Cycle mine, level 10. 
Fresh breccia with oxidized 
seams. Main clay seam as¬ 
says 300 ounces. All seams 
carry values. 

A few lodes, also, 


are associated with more curved and irregular Assuring than pertains to a sheeted 
zone, and might be called stringer lodes. This type, which is not characteristic 


4 















U. S. GEOLOGICAL SURVEY 


PROFESSIONAL PAPER NO. 54 PL. XIII 



VEIN STRUCTURE, CONUNDRUM MINE. 

Pieces of basic dike showing fluorite veinlets; pyrite disseminated throughout the rock. 










STRUCTURE OF THE GOLD DEPOSITS. 


161 


of tlie district, finds partial exemplification in the No. 1 Lee vein of the Portland 
mine. 

Among the numerous and important lodes coming properly under the desig¬ 
nation of sheeted zone, several structural varieties can be distinguished and are 
sometimes exhibited in different parts of the same lode. A common form is that 



Fig. 6.—Veins in Last Dollar mine. 1. Main vein, 40 feet above level 12. Typical sheeted and partly brecciated zone in fresh 
iatite-phonolite. Seams coated with quartz, dolomite, and calaverite. 2. Cross veins with medial vug holes, level 10. 
3. Vein, west drift, main cross vein, level 5, showing middle filled fluorite vein. 4. Cross vein No. 3, at east side line, level 5. 


characterized by the presence of two main parallel fissures, usually 3 or 4 feet apart, 
accompanied by less regular and less persistent fractures in the intervening and 
adjacent rock. As an example of this type may be cited the Legal Tender vein, in 
breccia, as seen on level 10 of the 
Golden Cycle (fig. 5), and the 
Doctor-Jackpot vein, also in 
breccia. The Gold Coin vein 
and A, B, and C veins of the 
Ajax mine show a similar struc¬ 
ture in the granite. 

In another common type of 
sheeted zone the parallel fissures 
are more numerous, and are 
spaced with some regularity, as 
illustrated in fig. 6. There is 
usually a medial portion of the 
lode, ranging from a few inches 
to a foot or two in width, within 
which the rock is divided into a 
large number of very thin plates 
by fissures often less than an 
inch apart. This band of in¬ 
tense sheeting is accompanied on 
both sides by parallel fissures 
which are spaced farther and farther apart, so that the sheeted zone as a whole 
merges gradually into the country rock. This type is well exemplified by the 
Howard fiat vein, in the southern part of the adit level of the Anaconda mine (fig. 7). 



10 


20feet 
i 


Fig. 7.—Structure of Howard flat vein, Anaconda mine, adit level. 
Illustrates close sheeting in middle part of vein, the fissures becom¬ 
ing gradually farther apart in the foot and hanging walls. 





























162 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


by other flat veins in the Mary McKinney mine and by the Doctor-Jackpot, Chance, 
Matoa, and many other lodes, particularly those in the breccia. 

There are a large number of sheeted zones in breccia and in granite, which are 
composed of many parallel or nearly parallel fissures, but which differ from the type 

just described in the absence of a well- 
defined medial zone and in the rather 
less regular character of the fractures. 
This type is admirably illustrated by 
the wider Captain veins in the breccia 
of the Portland mine, some of which 
are stoped to a width of 120 feet. It 
is not in these widest parts, however, 
that the sheeted structure is best seen, 
for in the large stopes the jointing, as 
appears in PL XV, B, is often so irregu¬ 
lar that the lode-like character is lost. 
In the narrower Captain veins, on the 
other hand, the fracturing as shown in 
PI. XIV and in fig. 8 retains the charac¬ 
ter of a sheeted zone. Fissures over 
half an inch in width are rarely seen in 
the Captain stopes and the ore often 
occurs in scarcely visible cracks. Other 
good examples of such broad zones of 
general sheeting are the Anaconda lode 
(PI. XIV) and parts of the No. 2 vein 
of the Mary McKinney mine. In the 
granite the sheeted zones, while similar 
in character to those just described in the breccia, are usually narrower. As exam¬ 
ples of this general type of structure in granite may be mentioned the Diamond 
vein in the Portland mine, the No. 6 
vein in Stratton’s Independence 
mine, the Granite vein, and the 
C. K. & N. vein. In the Ajax mine 
there is a peculiar association of a 
sheeted zone with the flat fissures, 
illustrated in fig. 9. These flat fis¬ 
sures carry ore for 30 or 40 feet from 
the main sheeted zone. 

There is sometimes one fissure 
of a sheeted zone which is distinctly 
larger than the others and which 
usually contains the richest ore. 

The dominant fissure of the C. K. & N. 
vein, for example, is in some places 4 
inches wide, and contains slabs of country rock which were loose before they were 
cemented by ore. The Pointer lode, in syenite, also has a dominant fissure which 



Fig. 8.—North face of No. 8 Captain vein, Portland mine, level 
fi, showing sheeting in brecei^ 



Fig. 9.—Sheeted zone and “ flats” of the Apex vein, Ajax mine. 































GEOLOGICAL SURVEY PROFESSIONAL PAPER NO. 54 PL. XIV 




VEIN STRUCTURE, PORTLAND MINE. SHOWING SHEETING OF BRECCIA 








STRUCTURE OF THE GOLD DEPOSITS. 


163 



Fig. 10.—Section of part of Blue 
Bird Vein, level 13, showing 
massive vein of quartz and 
fluorite between phonolite and 
breccia. 1. Breccia. 2. Mas¬ 
sive quartz and fluorite. 3. 
Fragment of breccia. 4. Dolo¬ 
mite veinlet. 5. Phonolite. 


in a few places is 5 inches wide, and veinlets of 2 inches in width are common in 
nearly all the large mines. 

Although the prevailing narrowness of the productive fissures is one of the most 
characteristic features of the district, there are not lacking numerous examples of 
fissures which opened to considerable width. The Blue Bird 
lode in some places contains a vein, 3 feet wide, of solid fluorite 
and quartz inclosing fragments of breccia (figs. 10 and 11). 

Parts of the Work vein, or Black vein, as it is called, in the 
Mary McKinney mine, consist of a foot of fluorite or vuggy 
quartz between well-defined walls, accompanied by parallel 
sheeting. The Howard flat vein, as exposed in the Ophelia 
tunnel, shows bj r its large vuggy cavities that it must origi¬ 
nally have been a sheeted zone with occasional openings 2 
or 3 feet wide. The cross veins of the Last Dollar mine are 
apparently not wery persistent, yet one of them on level 12 
showed a local gaping of the fissure walls to a width of 2 
feet. The cross lode on level 11 of the Findley mine has a 
middle vein of compact fluorite and quartz up to 15 inches 
wide, with a few small parallel seams on each side. The 
middle fissure of the Buena Vista lode contains in places a 
similar vein up to 6 inches wide. Portions of the Doctor- 
Jackpot lode and the Lead vein of the Moon-Anchor mine fill 
fissures which 'opened to widths of 6 inches or more. In 
some cases these wide fissures occur merely in portions of a lode which elsewhere 
shows close parallel sheeting. In other cases, such as the work vein, the presence 

of a fairly thick plate of quartz and fluorite, or of 
other vein filling, is characteristic of the lode. 

In the upper parts of some of the lodes, the 
original structure is obscured by oxidation, 
whereby the sheeted structure is often lost and 
the vein forms a clayey streak sometimes several 
feet wide. Within this zone may occur veinlets 
of kaolin or alunite up to a foot wide. The most 
conspicuous example of this alteration is the Wild 
Horse vein, which is entirely oxidized in its 
productive portion to a depth of 1,000 feet. It 
is a structureless clayey mass, up to 25 feet wide, 
with two or more well-defined but curved and 
irregular walls. These walls are not continuous, 
but die out in places and are succeeded by others. 

Although most of the veins show by their 
structure and by their failure to dislocate the 
various dikes and intrusive sheets which they 
cross that the opening of their fissures was not 
accompanied by noticeable faulting, there are a few lodes, such as the Bobtail vein 
in the Portland mine, the Mary McKinney vein, the Doctor-Jackpot vein, and the 
Gold Coin vein, which have a somewhat different character. 



3 -Ft. 


Fig. 11.—Structure of Blue Bird vein, level 9, 
showing filled fluorite vein in middle. 










164 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

The Bobtail vein is a sheeted zone that lor at least a part of its course follows 
an older fissure in the granite. This fissure is filled with breccia composed chiefly of 
granitic material. It is probable, however, that this breccia is formed of particles 
that were carried into an open fissure at the time of eruptive activity rather than 
to trituration of the fissure walls by great movement. 

Parts of the sheeted zone of the Mary McKinney vein contain a dominant 
fissure up to about. 5 inches in width, which is fdled with fragments of phonolite 
partially replaced by roscoelite and fluorite. In this case the movement along the 
fissure zone was sufficient, at least locally, to brecciate the sheeted phonolite. In 
the Wardel vein, in the Anchoria-Leland mine, the thinly sheeted breccia of the 
medial part, of the lode is in some places shattered, showing movement along the 
fissure zone. 

The Doctor-Jackpot lode exhibits slight slickensides along portions of its regular 
foot-wall fissures. The displacement, however, is probably slight, as great move¬ 
ment could hardly fail to brecciate the thin sheets of the fissure zone. There has 
evidently been some movement along the Mattie D. vein of the Doctor-Jackpot 
mine, as shown by brecciation along the foot-wall fissure. The Cardinal vein, a 
crushed zone 1 foot wide in granite, shows well-defined horizontal slickensiding 
along the hanging wall on the 200-foot level. In parts of the Gold Coin vein, near 
the north end of the mine, the closely sheeted granite grades into brecciated material 
3 or 4 inches wide. The movement necessary to effect this brecciation of the thin 
laminae of rock was probably slight and was certainly local. 

The structures thus far described are those associated with lodes traversing 
large masses of uniform rock, such as breccia, latite-phonolite, syenite, or granite. 
Many of the fissures, however, pass from one rock into another or follow dikes and 
it is necessary to briefly note the structural details connected with such associations. 

The phonolite dikes have a general tendency, as is revealed by weathering, to 
split into thin slabs roughly parallel to the dike walls. Fissuring along the line of 
such a dike merely accentuates this inherent structure, and forms a well-defined 
sheeted zone which may involve the whole width of the dike or may constitute a 
narrow zone along one or both w r alls. A considerable number of the lodes in the 
district are wholly or in part sheeted phonolite dikes. As examples, may be men¬ 
tioned the Independence and Port land veins and the Cobb vein of the Moon-Anchor 
mine. A number of other lodes, such as the Apex vein of the Ajax mine, lie in the 
breccia or granite alongside phonolite dikes. 

In those cases where a fissure zone and a dike or mass of phonolite intersect 
nearly at a right angle, the platy parting of the phonolite tends to destroy the regu¬ 
larity of the sheeted zone. Thus the Walter vein of the Elkton mine, which in the 
breccia is a regular sheeted zone, becomes very irregular in the masses of phonolite 
described on page 333, and splits up into fissures running in various directions, many 
of them being nearly horizontal. The Spur and Coin veins of the Gold Coin mine 
also lose their regularity and become indistinct in an intrusive phonolite sheet which 
they cross near level 6. In the Isabella mine the Cheyenne vein, below level 10, 
and the Empire No. 2 vein, on level 11, become small and barren seams when they 
enter phonolite. 



U. 8. GEOLOGICAL SURVEY 


PROFESSIONAL PAPER NO. 54 PL. XV 


A 



VEIN STRUCTURE, LEVEL 4, PORTLAND MINE. 

A Stope on No 5 Captain vein, showing width of ore. 

11. Stope on Nos. 4 and 5 Captain veins, showing wide sheeting, scarcely distinguishable from ordinary jointing. 















STRUCTURE OF THE GOLf) DEPOSITS. 


165 


Productive fissure zones along basic dikes are in a general way similar to those 
along phonolite dikes. The basic dikes, like the phonolite dikes, readily develop 
platy parting parallel to their walls (PI. XVI, Ii). As a rule, however, the fissures in 
the “basalt” are smaller than those in phonolite, and in some cases, as in parts of 
the Conundrum lode, may form an exceedingly complicated network, as shown in 
PI. XIII (p. 160). 

Some sheeted zones, at the point where they cross a contact between two rocks, 
such as breccia and granite or breccia and phonolite, expand in one or both of the 
rocks into a network of irregular fractures. Such a mass of irregular fissures occurs 
in the granite of the El Paso mine, where the El Paso vein crosses from granite into 
a phonolite dike, and forms an important ore body described on page 354. Some of 
the ore bodies in the Prince Albert and Dead Pine mines are similarly related to the 
intersection of a fissure zone with a contact plane. 

INTERSECTIONS. 

The crossing of one fissure zone by another is a common occurrence in the 
Cripple Creek district, notwithstanding the general' radial arrangement of the most 
important lodes. Often the intersecting fissures have a strike nearly at right angles 
with the main fissure zone and are then usually known as cross veins. In other 
cases the strikes of the intersecting fissures are less than 45° apart and the shorter 
lode is often called a spur vein. In still other crossings the intersection is between 
a nearly vertical fissure zone and a so-called fiat vein. 

In most cases the fissures intersect without noticeable displacement of one by 
the other, a fact that is in full harmony with the usually very slight movement along 
the fissures indicated by their structural peculiarities. The rock near the inter¬ 
section, however, is often irregularly fissured and in many instances constitutes an 
ore body, so that the details of the crossing are not always clear. Intersections 
without visible fault displacement are so numerous that only a small number of the 
observed examples can be here given. Many additional occurrences are noted in 
the detailed descriptions of the mines. 

In the northern part of the Mary McKinney mine (see fig. 32, p. 323) the Mary 
McKinney, No. 1, No. 2, No. 4, No. 6, Black, No. 3 fiat, No. 5 flat, and other veins 
intersect at various points without faulting. Near many of the intersections the 
rocks are traversed by subsidiary fractures containing ore and forming with the 
main fissures some of the widest ore bodies in the mine. In Stratton’s Independence 
mine the flat vein, a nearly horizontal sheeted zone, is crossed by the fissures of the 
Independence lodei The conditions for detecting the occurrence of any displace¬ 
ment are here unusually favorable, but no faulting is apparent. In the northern 
part of the mine the Independence, Bobtail, Emerson, Grant, and other lodes all 
converge in a general way so as to meet the similarly converging Bobtail, Diamond, 
and No. 2 veins of the Portland mine. These lodes come together in a region of 
very complex Assuring, in which, however, there is no evidence of appreciable 
faulting. The Abe Lincoln, Anchork-Leland, Midget, and Anaconda mines all 
afford examples of fissure zones intersecting without faulting. 

There are a few cases, however, of one fissure faulting another. Some of the 
faulting fissures are productive. Others are barren and usually contain soft clay¬ 
like omime. In the Anchoria-Leland mine the fissure zone known as the Fault vein 

O o 


166 GEOLOGY AND GOLD DEPOSITS OF THE CKIPPLE CREEK DISTRICT. 

usually contains one or more seams of gouge carrying a little pyrite, but no ore. It 
slightly offsets the City View dike and perhaps also the Chance and Matoa lodes. 
(See fig. 25, p. 293.) The displacement is probably less than 6 feet. In the southern 
part of the Mary McKinney mine, the Mary McKinney fissure zone faults a generally 
barren cross fissure known as the Jackpot vein, though it is not the productive lode 
known in the Doctor-Jackpot mine. The throw in this case corresponds to a reversed 
or thrust fault and can scarcely exceed 15 feet. In the Elkton mine the Elkton or 
Walter lode is slightly displaced near the breccia-granite contact by the barren fissure 
known as the Dead vein, or better as the Thompson fault. In some places this is a 
simple fissure containing a foot or more of soft slickensided gouge. Elsewhere it 
consists of two or more narrower fissures filled with similar material. The net 
displacement, though not susceptible of measurement, is probably not over 100 
feet and may be very much less. 

Some slight faulting was noticed in the Jerry Johnson and W. P. TI. mines, a 
flat vein in one place having displaced the W. P. H. vein for a few feet. The 
Shurtloff vein faults a prominent cross vein on level 11 of the Findley mine, the east 
part being thrown 6 feet northward. In the Isabella mine, on level 11, the north¬ 
west-southeast Pinto basic dike is faulted by the nearly east-west Empire No. 2 
vein, the southeast part of the dike being thrown 10 feet to the east. In the same 
mine the Buena Vista vein, striking northwest, is apparently faulted by the Klon¬ 
dike vein, the southeast part of the Buena Vista being offset from 20 to 50 feet to 
the southwest. It is possible in this case, however, that both fissures were formed 
at the same time and that the Buena Vista vein is merely deflected from one sheeted 
zone to another. The Pharmacist vein, striking 60° E. and dipping northwest 
at 60°, is faulted by the Zenobia vein striking from N. at 20° E. to north-south 
and dipping west at from 60° to 80°. The east part of the Pharmacist is offset from 
10 to 20 feet to the southeast. Both are productive lodes. Their intersection 
pitches north and is exposed to a depth of several hundred feet in the Zenobia 
incline. 

In the El Paso mine the nearly east-west C. K. & N. lode is intersected by 
fissures having general northeasterly strikes and roughly parallel with the El Paso 
and Tillery veins (fig. 39, p. 350). Some of these fissures do not visibly offset the 
C. K. & N. vein. In one case the ore of the C. Iv. & N. vein turns and follows one 
of these cross fissures for about 100 feet and then resumes its normal course. In 
another case the C. K. & N. vein is offset for about 100 feet, the intersecting fissure 
containing no ore. This may possibly be a fault, formed after the deposition of the 
ore in the C. K. & N. vein; but it is more probable that the offsets in the C. K. & N. 
fissure zone are due to the fact that it w r as formed in rocks already traversed by 
the northeasterly fissure zones of which the El Paso lode is the most prominent 
member. That is, it is in the main an original structure and is not due to faulting 
after the deposition of the ore or even after the formation of the C. Iv. & N. fissures. 

In the Gold Coin mine there is a prominent fissure zone known as the Cashen 
fault, which strikes N. 20° E. and dips nortKvest at 51°. It contains in places 
from 4 to 5 feet of crushed and altered country rock forming a soft clayey gouge, 
and has the appearance of a fault of considerable throw. Nevertheless the Coin 
lode and the Montana phonolite dike, both of which are intersected by the Cashen 


GEOLOGICAL SURVEY PROFESSIONAL PAPER NO. 64 PL. XVI 



VEIN STRUCTURE 













STRUCTURE OF THE COLD DEPOSITS. 167 

fault, show no noticeable displacement. The net throw of the fault must be very 
small and the dislocation may be older than the fissure zone of the Coin lode. 

ORIGIN OF FISSURES. 

It has been shown that the principal fissures are confined to an area little larger 
than that of the Cripple Creek volcanic neck ; that they have a general radial arrange¬ 
ment, and that their formation was accompanied by very slight faulting. It appears 
further that the basic dikes have a similar radial grouping; in fact, the fissures 
occupied wholly or in part b} r dikes and those occupied by ore are so similar in 
character and so closely related in direction and distribution that they were probably 
formed in the same manner, if not at the same time. 

The basic dikes and the ore-bearing fissures are younger than any of the phono- 
lite intrusions and originated after the volcanic breccia had been cemented into a 
firm rock. The sheeted zones were certainly formed in part before the intrusion 
of the basic dikes. This is clearly shown in the Granite mink, where a “ basalt ” dike 
turns from one fissure to follow the Bobtail lode, and in the Elkton mine, where 
parts of the Raven lode consist of a zone of sheeted breccia from which the “ basalt’’ 
dike is locally absent. Had this sheeting been produced after the intrusion, the 
dike should be fissured like the breccia. This, however, is not the case. The 
sequence of events seems to have been as follows: (1) Sheeting of the indurated 
breccia, (2) intrusion of basic dikes along parts of the sheeted zone, (3) slight 
Assuring of the dikes, probably in part by mere contraction in cooling, whereby 
they were divided near the walls into thin plates, and (4) ore deposition. That 
the breccia had been much fissured and even shattered before the basic intrusions 
and that all of the resulting fissures were not fdled by the dikes is well shown in 
the Moose mine. It is probable that some sheeting followed the basic intrusions, 
but it is rarely possible to distinguish this from the earlier Assuring. We may 
conclude, then, that some of the productive Assures were formed before the basic 
intrusions, that some were formed after the intruded rock had solidiAed, and that 
Assuring and intrusion were closely associated in point of geological time. 

The character of the Assures is suggestive of fracturing under light or moderate 
load. Facts supporting this suggestion are (1) the greater number and width of 
the Assures near the surface, (2) the branching of the upper parts of some Assures, 
such .as the Bobtail veins in Stratton’s Independence mine, and (3) the change in 
dip of some Assures, the superAcial portion having usually the Aatter dip. Though 
at Arst glance the generally small size of the openings produced by the Assuring 
might be considered as indicative of fracturing under heavy load, yet the explana¬ 
tion of this feature is thought to be that the fracturing stresses were relieved by 
comparatively slight deformation of the rigid rock mass. Had the stresses been 
regional instead of conAned to the volcanic neck the initial fracturing might have 
been followed by considerable faulting along the Assures before equilibrium was 
restored. 

The conclusion that the Assures were formed under relatively light load does 
not rest entirely upon the study of the Assures, but is supported by general geological 
considerations relating to the development of the present topography, as shown 
on page 36, and by the distribution of pay shoots, as suggested on page 215. 


168 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


The areal distribution of the fissures, their radial plan, and their connection with 
the basic dikes show that they were produced by local rather than regional stresses. 
It is true, as Penrose has shown, that the granite of the prevolcanic plateau is con¬ 
spicuously sheeted at points distant from the productive area, as in Eightmile Can¬ 
yon, but this sheeting is associated with no known ore deposits and is not clearly 
related to the Assuring of the Cripple Creek district. It seems most reasonable to 
regard the Cripple Creek fissures as having some genetic connection with the local 
volcanic center. 

The nature of the stresses that fissured the rocks is not easily determined. The 
character of the Assures shows that the stresses were of a kind that could be relieved 
by comparatively slight strain. The rocks were in most places merely fractured and 
not noticeably displaced. Had the tangential movement along the Assures been 
greater it might have supplied a clue to the directions and character of the forces that 
produced the faulting. In the present case, however, the tacts do not enable us to 
decide with certainty which of a number of hypotheses is applicable. The incon¬ 
spicuous character of the Assures, their radial disposition, and the absence of notable 
faulting suggested at one period in their study earthquake shocks, emanating from 
some point under the central part of the district, as a possible explanation. It is 
diAicult, however, to account by this hypothesis for the characteristic sheeted struc¬ 
ture of the lodes, which seems to demand an explanation involving compressive 
stresses. The hypothesis which on the whole seems most in harmony with the facts 
is that the entire mass of breccia and volcanic rocks, after the phonolitic eruptions 
had ceased and the breccia had become Armly cemented, settled down very slightly 
within the steep-walled volcanic funnel in the ancient rocks of the plateau. As the 
walls of the volcanic neck are somewhat irregular and as in general they converge 
downward, such slight sinking, by forcing a rigid mass to adjust itself to a slightly 
smaller space of different shape, would produce compressive stresses in the subsiding 
mass and to some extent in the inclosing granitic rocks. The stresses would be 
relieved by fractures characterized by their number and by diversity of trend rather 
than by great size or by conspicuous faulting. The amount of settling necessary to 
produce Assuring of the kind found in the district would be extremely slight and need 
call for no greater faulting along the general line of the granite-breccia contact than 
is known to exist. 

This hypothesis also affords an explanation of the observed relation between the 
Assuring and the basic dikes. The dikes may be regarded as the Anal magmatic 
residuum of the volcanic reservoir, squeezed quietly into some of the Assures formed 
by the slight settling of the solidiAed products of earlier eruptions. Fissuring and 
the intrusion of the basic dikes, according to this hypothesis, are genetically related 
and represent the dying out of the volcanic forces. They were the Anal structural 
manifestations of volcanism and were succeeded by gaseous and aqueous emanations 
and by ore deposition. 

It is possible that the removal by erosion of the volcanic cone that in late Ter¬ 
tiary time covered the central part of the Cripple Creek district may have resulted in 
some readjustment of the rocks relieved of this local load. While it does not seem 
that such unloading could initiate the formation of the ore-bearing Assures, it may 
have increased their width. 


CHAPTER VIII.—THE ORES. 

GENERAL CHARACTER. 


The characteristic feature of the Cripple Creek ores is the occurrence of the gold 
in combination with tellurium, chiefly as calaverite, but partly also as the more 
argentiferous sylvanite, a and probably to a minor extent as other gold, silver, and 
lead tellurides. Native gold appears to he absent from the telluride ores, except as it 
may be set free by the oxidation of these tellurides. Pyrite is widely disseminated 
through the country rock and also occurs commonly in small amounts in the fissures, 
associated with tellurides. Galena and sphalerite are sparingly present in the major¬ 
ity of the veins. Tetrahedrite, or gray copper ore, and stibnite are of frequent occur¬ 
rence. Molybdenite in small quantities is probably always present. The tetrahed¬ 
rite is usually rich in silver, and also contains gold. Possibly, however, the latter 
metal is due to admixed calaverite, as the two minerals often are found in intimate 
intergrowth. The galena and zinc blende rarely contain enough of the precious 
minerals to form ore. Auriferous pyrite is often reported, but in the cases investi¬ 
gated the gold was found to be derived from admixed tellurides (p. 170). Metallic 
minerals found only as great rarities are hubnerite, specularite, chalcopyrite, chal- , 
cocite, and arsenopyrite. 

The usual gangue minerals of the ores are quartz, fluorite, and dolomite; more 
rarely chalcedony and opal. Roscoelite and rhodochrosite are also found in a few 
places. Celestite, the sulphate of strontium, occurs as little acicular crystals in quartz 
vugs and forms the gangue of some exceptional veins. Calcite occurs interstitiallv 
in much of the breccia near the ore bodies, hut is rarely found in distinct crystalline 
form with the ore minerals. Secondary potassium feldspar (adularia or valencianite) 
is common in the ores. It is especially abundant in the ores inclosed in granite, par¬ 
ticularly those in the Pikes Peak type. 

Owing to the occurrence of the ore minerals and gangue as the filling of narrow 
fissures, joints, and cracks in the sheeted zones which usually constitute the lodes, or 
as a very incomplete replacement of the country rock, the ores of Cripple Creek as 
mined have approximately the composition of the somewhat altered rocks which 
immediately adjoin the veins. The quantity of metallic or gangue minerals is thus 
in nearly all cases relatively insignificant. By reason of the slight metasomatic alter¬ 
ation the rocks in the lodes approximate somewhat closely to the normal composition 
of the fresh country rock, be it granite or any of the volcanic rocks of the district. 

Oxidized ores, while still worked in many properties, are of relatively less impor¬ 
tance than when Penrose described the district. They contain the characteristic dull 
gold, often in pseudomorphous skeletons, resulting from the oxidation of the tellu¬ 
rides, associated with tellurite (tellurium dioxide), emmonsite or durdenite (both 

a Calaverite, (Au, Ag) Tea; tellurium, 57.4 per cent; gold, 39.5 per cent; silver, 3.1 ner cent. Sylvanite, (Au, Ag) Tea? 
tellurium, 62.1 Der cent; gold, 24.5 percent; silver, 13.4 per ceDt. 


169 



170 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

hydrated ferric tellurites . and probably other oxidized compounds of tellurium and 

iron. These minerals occur in association with kaolin, alunite, and ferruginous clays, 

which result from the oxidation of the country rock in which the vein is contained. 

The deep workings of the present day show that kaolin is always connected with 

oxidation, and is not a product of the original mineralization of the district, as was 

supposed bv Penrose. _ 

COMPOSITION AND VAI/CTE. 

Gold and silver are the only metals utilized in the Cripple Creek ores. The 
small amounts of copper, molybdenum, antimony, lead, and zinc are of no economic 
importance. Tellurium is likewise allowed to go to waste, as there is insignificant 
demand for it and its recoverv would be verv costlv. The average amount of gold in 
the ores is probably between 1.5 and 2 ounces, or from $30 to $40 per ton. In some 
of the larger mines the average value sinks to 1.25 ounces or even 1 ounce per ton, 
the latter figure corresponding to 0.0035 per cent. From a lower economic limit of 
about $12 per ton the values of individual shipments swing through a wide range up 
to ores carrying $5,000 or even $50,000 per ton. A shipment of 274 tons from level 
10 of the Cheyenne vein. Isabella mine, yielded $219,000, according to reports, and 
in 1904 a shipment of 2.901.42 pounds of El Paso ore afforded on assay 2.592.68 
ounces of gold and 299.33 ounces of silver per ton and yielded $75.24S.79 net. or over 
8 per cent gold. This would indicate that one-third of the cpiantity consisted of pure 
calaverite. on the assumption that this was the only auriferous mineral‘present. 
Oxidized ores which contain free gold only may under favorable circumstances be 
subjected to direct cyaniding and yield a profit with a tenor in gold of about $5. 

The statement is often made that some of the pyrite in the veins contains high 
gold values. In most cases this is due to admixed telluride. Penrose 0 leans 
toward the same view and states that two pure crystallized specimens examined by 
Hillebrand did not contain a trace of gold. A sample was taken of a heavy sul¬ 
phide filling in a cross vein on level S. Last Dollar mine. The vein was several 
inches wide, and consisted of granular pyrite and sphalerite, with a little molyb¬ 
denum. lead, and copper. An assay by Dr. E. T. Allen and a determination of 
tellurium by Hillebrand gave Te. 0.016 per cent: Au, 0.0015 per cent (0.44 ounce 
per ton : Ag. 0.017 per cent (4.9 ounces per ton). The molecular ratio is 126 Te : 7 
Au : 157 Ag. corresponding approximately to a proportion of 42 sylvanite [(Ag. Au) 
Te,] and 225 liessite (Ag,Te\, leaving a surplus of 23 Te. which might possibly 
belong to lead or some of the other baser metals. The pyrite evidently contains 
no gold. 

The pyrite of the altered country rock is always poor in gold. A specimen of 
coarse pyrite with sphalerite from the breccia in the Hull City mine, level 7. near 
Vindicator line, contained only 0.20 ounce of silver and 0.04 ounce gold per ton. 
Whether free gold is present in the telluride ores is a debatable cjuestion. It 
may and probably does occur locally, but it is likely to be in very small amounts. 
Analyses 2 and 3 of the table below show that a small part of the gold in the tellu¬ 
ride ore from the El Paso mine, presumably entirely free from oxidation, would be 
free gold if all of the silver were assumed to be present as tellurides. But as there 


c Mining geology of the Cripple Creek •listrict, Colorado: Sirt -enth Ann. Rept. U. S. Geol. Survey, pt. 2,1SQ3, p. 122. 



o \tp> 'in >>' and value >f the --res. 


171 


is probably some silver mineral present, possibly tetrahedrite. which is known to 
occur at the El Paso—a surplus of silver may belong to this, and the gold and 
tellurium, with some silver, would combine to form calaverite without free gold. 
As is well known from other mining districts, especially Kaigoorlie. free gold may 
occur in considerable quantities with tellurides. 

The Cripple Creek ores, as a rule, contain very little silver, the averse propor¬ 
tion being about 1 ounce of silver to 10 ounces of g Id. In the Portland and Strat¬ 
ton's Independence mines the proportion is very much less, the silver from the 
Portland in 1901 amount ins: t only 2.4 ounces for each It ounces :f : Id. Rich 
parcels of gold ores often contain a surprisingly small quantity of silver. In the 
shoot on the 245-foot level in the W. P. H. mine even the richest ore. valued at 
several thousand dollars per ton. contained but a few ounces of silver per ton. The 
“fines from the El Paso mine analyzed by Hillebrand and Alien/ which were 
practically free from oxidation, contained from 2.19 to 3.00 ounces silver against 
14.53 to 19.63 ounces gold. In the Blue Bird. Doctor-Jackpot. Conundrum. Pointer, 
and other mines containing n -table am. tints of tetrahe* irite or ral-na :he : r -por¬ 
tion of silver rises considerably above the average. Very rarely small lots f ore 
contain a higher value in silver than in gold. A shipment of 1.000 pounds of gray 
copper ore from the Accident mine contained 2.500 ounces silver and 25 ounces 
gold per tt>n. Somewhat similar silver ore occurred in the Pointer mine. A recent 
shipment from the Red Spruce min e on Gold Hill is stated to have contained 
50 ounces of silver and $5 in gold per tonb 

That the average tenor of the ores of Cripple Creek is decreasing: somewhat is 
an unquestionable fact. Penrose says that the average value : ill re shipper up 
to 1S94 would be between $50 and $85 per ton. The Mint report for 1S97 p. 122 
states that the average value lies between $35 and $40 per ton. while in me same 
report for 1899 (p. 99) $45 is given as the average value of the ore. At the present 
rime it is from $3‘! to $4 oer ton. The early figures of IS94 may be lisregardei. 
since high expenses and excessive freight prohibited the snipping : 1* w-graae re. 
The Portland data show a very decided decrease, as f- 11 ws: 

Tenor faSd arejfrvm PorLxnd mime. 



Per son. 


Ber He. 

1SS4.. 

.. $71.00 

1900 ... 

.£36 00 

lv 

... 5L 00 

1908.... 

. 29.0*0 

1047 

... 60.00 

19*34.. 

_ 36.92 

1900... 

... 30.00 

19*35__ 

.. 23.60 


A value of $30 may represent the average of some >5 the largest mines, but 
most of the smaller ones and many of the large ncs 'hip ore much richer man Has. 
Some of the decrease is unquestionably caused by lowered operating and reduction 
expense', and it is doubtful whether more than a small fraction should be barge 1 
to the actual falling off of values in depth. If this really takes place, ii is prob¬ 
able due to a slightly lower tenor in the unoxidized ores than in these which Lave 
been subjected to oxidation. 


* BsiL IT. S- CeoL Sarwey No. p. K 

i V — tr.i Set. Press. Saz Fnmeiscr Oct.Oer L. 

- rjciesirii x- - Rape. U- S- »>roi. Srurr--. pc. — HO. p. . 2. 


















172 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


Chemical analyses of Cripple Creek ores. 



1. 

II. 

III. 

IV. 

V. 

VI. 

VII. 

Silica. 

57.81 

54.91 

54.68 

55.98 

59.12 

56.70 

59.58 

'Alumina. 

20.13 

17.80 

17.87 

17.09 

18. 77 

19.35 

16.00 

Iron. 


4.80 

5.30 

3. 44 

3.38 

4.20 


Magnesia. 

.86 

.36 

.20 

.47 

.32 

.37 

.03 

Lime. 

1.32 

2.04 

2. 65 

.71 

.38 


2.03 

Alkalies. 

10.53 

12.00 

12.00 



13.97 

12.91 

Manganese dioxide. 

.31 

.66 

.94 





Barvta. 

.22 




I 

. 11 

Titanium dioxide. 

.66 



1 

.75 

Copper. 

.0064 

Trace. 

Trace. 





Lead. 

.0071 

Trace. 






Zinc. 


.60 

.64 





Arsenic. 

.0944 



i 



Tellurium. 

.0152 

Trace. 

Trace. 


. 10 


Molybdenum. 

.0368 






.01 

Sulphur. 


2. 49 

2. 25 

1. 77 

1.23 

4. 75 


Carbon dioxide. 


2.00 





.26 

Fluorite. 

.68 






1. 42 

Pyrite. 

2.50 






. 4. 78 

Barium sulphate. 


. 18 

.24 





Combined water. 

.93 





. 50 

. 81 






1 



I. Ore beds of United States Reduction and Refining Company, Standard mill, Colorado City, February, 1904. 

II. O re bed 91, Portland mill, Colorado City. Average silver one-fourth ounce per ton. 

III. Ore bed 91b, Portland mill, Colorado City. Average silver one-fourth ounce per ton. 

IV. Golden Cycle ore, 300 tons. Analysts, Von Schulz & Son. Gold 0.98 ounce, silver 0.62 ounce per ton. 

V. Golden Cycle ore, 600 tons. Analysts, Von Schulz & Son. Gold 1.52 ounces, silver 1.04 ounces per ton. 

VI. Specimen Moose ore. Analyst, F. C. Knight. Gold 12.24 ounces, silver 6.70 ounces per ton. 

VII. Granite ore, Ajax mine. Analyst, W. F. Hillebrand. 


'Analysis I represents mixed ores, oxidized to some extent and derived both 
from breccia and from latite-phonolite. Analyses II and III represent the normal 
ore from the Portland mine, largely in breccia country rock and slightly oxidized. 
Analyses IV and V show average Golden Cycle ore, largely from veins in breccia 
and mostly oxidized. These analyses substantiate the statement made that the 
ores, speaking approximately, have the same composition as the country rock, the 
only notable exception being the granite ore, which is very low in silica compared 
to the unaltered rock. The amount of pyrite varies from 2 to 5 per cent, the 
latter figure being rarely exceeded in the average composition. Fluorite is always 
present, but the amount is not often more than 2 per cent and is commonly much 
less. One or two per cent of carbon dioxide is ordinarily present. Copper, lead, 
zinc, and molybdenum, with arsenic and antimony, are present in most cases, 
but the quantities are insignificant. Bismuth and vanadium have been found in 
ores from Stratton’s Independence mine. 
































































MINERALOGY OF THE FISSURE FILLINGS. 


173 


The following very carefully made determinations of the metallic contents of 
rich ores should be added: 

Partial analyses of ores from Cripple Creelc. 



i. 

• 2. 

3. 

Gold. 

0.35 

0.0506 

0.060 

Silver. 

None or trace. 

.0075 

.0103 

Copper. 

.03 

.0059 

.0070 

Lead. 

o.l8 

Bismuth. 

.0025 


Molybdenum. 

.018 

.0015 

.0018 

Tellurium. 

.0742 

.092 

Tellurium dioxide. 

.36 





a From another sample of same class of ore. 


1. Oxidized ore from 100-foot level of Stratton’s Independence mine. Analyst, W. F. Ilillebrand. Mine assays give 107 
ounces gold per ton. 

2. Telluride ore, El Paso mine. Au and Mo determined on 100 g.; Te on 50 g. Analyst, W. F. Ilillebrand. Results of 
assays: 2.19 to 2.07 ounces Ag, 14.53 to 15.60 ounces Au, per ton. 

3. Similar ore, El Paso mine. Analyst, W. F. Hillebrand. Results of assays: 2.87 to 3.00 ounces Ag, 17.75 to 19.63 ounces 
Au, per ton. 

xVccording to Mr. G. D. Doveton,® the ores as prepared for shipment have a 
composition within the limits indicated in the following table: 


Si0 2 . 60 -70 

A1 2 O s . 16 -23 

CaO. 1 - 5 

MgO. 0.1- 0. 3 

BaO. 0. 0- 0. 25 

Fe. 1.5-10 

S... 1.5- 5 


Limits of composition of Cripple Creek ores. 

Mn. 

Cu. 

Te. 


Zn. 

As. 

FI. 

Na.,0+K. 2 0. 


Pb. 


0 . 0 - 


Zb 


The maxima given for copper and arsenic occur very rarely. 

TIIE FISSURE FIEEENGS. 


0 . 0 - . 10 
0.0- 2. 5 
Trace- . 01 
0 . 0 - .1 
0.0- 2. 5 
0 . 0 - 10.0 
4.0-12.0 


MINERALOGY. 


The most abundant mineral in the fissure fillings or veins is quartz. It is in 
nearly all cases associated with fluorite, whose purple color often renders it more 
conspicuous than the quartz, even when the latter predominates. Much of the 
so-called fluorite, or “purple quartz,” of the veins, such as occurs in great abundance 
in the Blue Bird vein and in the Black or Work vein of the Mary McKinney mine, is 
ji finely crystalline aggregate of both minerals. The relative abundance of the 
quartz and fluorite varies greatly in different lodes and even in different parts of the 
same lode. Dolomite, though not present in all of the veins, is in many places an 
important gangue mineral. It is especially abundant in the Hidden Treasure and 
other veins in the northern part of the Portland mine and in the Vindicator, Mary 
McKinney, and Last Dollar mines. 


a Min. Jour. (London), December 23,1905. 


13001—No. 54—06-13 














































174 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


Pyrite occurs in all of the lodes, often intimately associated with the rich tellu- 
rides. It is sometimes supposed to be auriferous, but tests made on pyritic ores 
have in all cases shown the presence of tellurium, and careful chemical examination 
of pyrite crystals (see p. 170) has failed to detect a trace of gold. It is probable, 
therefore, that the pyrite of the Cripple Creek veins merely plays the part of a 
gangue mineral. The gold found in such pyritic ores as are stoped in the Lee and 
Lost Anna veins in the Portland mine and in the Elkton, Last Dollar, and Gold Coin 
mines probably occurs as a telluride mechanically inclosed in the pyrite. In a 
polished specimen of ore from the C. Iv. & N. mine such a relation of calaverite and 
pyrite is clearly visible (fig. 13, p. 181). 

Sphalerite, while not on the whole so abundant as pyrite, is present in nearly 
all the veins, and in some, such as the Bonanza King (Midget mine), Conundrum, 
and Lead (Moon-Anchor mine) it is found in considerable quantity. Bunches of 
galena and sphalerite in the Conundrum vein are in some cases several feet long 
and up to 6 inches wide. Usually, however, sphalerite is an inconspicuous con¬ 
stituent. The ore of the Portland mine contains about 1 per cent of zinc blende, 
and this is probably over rather than under the general average for the district. 

The distribution and occurrence of galena are much like those of sphalerite. 
Small quantities can be detected in many of the lodes, and it is probably present as 
invisible particles in others. Occasionally, as in the Pointer, Conundrum, Bonanza 
King, and Lead veins, it forms a notable proportion of the ore, which in such places 
is usually of low grade. Sporadic bunches of galena occur, however, in close asso¬ 
ciation with the rich auriferous tellurides, as in the Abe Lincoln mine. 

In addition to quartz, fluorite, dolomite, pyrite, sphalerite, and galena, which 
in varying proportions are the usual mineralogical associates of the tellurides, the 
lodes contain numerous other minerals which are less abundant. Among these are 
tetrahedrite, which has been noted in over 20 veins in the district (see p. 121), and 
molybdenite, which, while rarely conspicuous, frequently accompanies the tellurides 
and has been identified in many of the mines. Stibnite has a similar association 
with the rich ores and is probably present in small quantity in most of the promi¬ 
nent lodes. Chalcopyrite, in other regions so often accompanying pyrite, sphaler¬ 
ite, galena, and tetrahedrite, is remarkably rare in the Cripple Creek district and 
was noted only in the Blue Bird mine. Hubnerite occurs in the Puzzle vein (cut 
by the Ophelia tunnel), but, so far as known, nowhere else in the district. 

Among what are usually termed the nonmetallic vein minerals are some which, 
while not so abundant as quartz, fluorite, or dolomite, are yet characteristic of the 
Cripple Creek veins. Such a mineral is celest.ite, which has been noticed in slender 
prisms in a large number of the veins. Hollow pseudomorphs of quartz after this 
mineral are common in most of the prominent lodes. Orthoclase, as a vein mineral, 
is fairly common in the lodes, although it is especially characteristic of the meta- 
somatic ores in granite. Roscoelite occurs as a gangue mineral in the Mary McKin¬ 
ney and Ajax mines and probably elsewhere in the district. Chalcedony and opal 
are not uncommon as films and crusts lining quartzose vugs. Rhodochrosite occurs, 
so far as known, only in the Pointer, Moon-Anchor, and Fluorine mines. Calcite 
and barite, both common vein minerals in other districts, are rarely found in the 


MINERALOGY OF THE FISSURE FILLINGS. 


175 


Cripple Creek lodes. Biotite, associated with pyrite, is known only in the abnormal 
Dolly Varden vein where exposed in the Ophelia tunnel. 

The gold in the unoxidized ores of the lodes occurs in combination with tellurium 
as calaverite, sylvanite, or krennerite. Calaverite is the most abundant telluride 
of the three, krennerite being apparently the least common. The identification of 
the various tellurides usually requires refined crystallographic and chemical work, 
though calaverite can sometimes be distinguished from sylvanite by its more yellow 
color. As such refinement is not practicable in every case, the relative abundance 
of the three species, particularly of krennerite and calaverite, which have approxi¬ 
mately the same composition, remains somewhat in doubt. The occurrence of 
native gold, while not unknown in the unoxidized parts of the lodes, is so rare as to 
be regarded as a curiosity. 

For more detailed descriptions of the minerals occurring in the lodes, and for 
an account of the products resulting from the oxidation of the original fissure 
fillings, the reader is referred to the sections on the mineralogy of the district and on 
the processes of oxidation. 

The order in which the vein minerals were deposited (paragenesis) is not the 
same in all fissures nor even in all parts of one fissure. In many of the lodes, more¬ 
over, a mineral which was deposited near the wall and which therefore belongs to 
an early stage in the process of vein growth occurs also in the vugs along the medial 
portion of the crustified vein. Pyrite, for example, while in many cases one of the 
earlier of the vein minerals, is sometimes found in small crystals implanted upon 
the quartz, fluorite, or dolomite which line the vugs, and in the C. Iv. & N. mine it 
incrusts crystals of calaverite. Other minerals which are known to have formed 
successively in the same vein are quartz, fluorite, sphalerite, and tetrahedrite. 
As a general rule the tellurides were formed during the later stages of fissure filling, 
as is shown by their prevalent occurrence as projecting crystals in the vugs. Occa¬ 
sionally, however, tellurides have crystallized simultaneously with quartz, fluorite, 
or dolomite at an earlier stage, so that they are embedded in a compact gangue of 
one or more of these minerals, as in the El Paso and C. K. & N. mines. Sphalerite 
and galena, occasionally associated with barite, as in the Tillery vein of the El Paso 
mine, are usually older than any tellurides that may accompany them, although in 
the Abe Lincoln mine the difference in age seems to be slight. Dolomite, fluorite, 
and quartz are frequently intercrystallized in a way to show that they were formed 
at the same time. In some cases a definite sequence is discernible, as in the Hidden 
Treasure vein, where fluorite w r as followed by dolomite and dolomite by quartz. 
In other cases, as w r as observed in ore from the Findley mine, dolomite is incrusted 
by fluorite. Specimens from the Doctor-Jackpot vein show 7 an early crystallization 
of pyrite and tetrahedrite, followed by dolomite upon which tetrahedrite occurs 
again as implanted crystals, followed by celestite, quartz, and pyrite in the order 
named. While celestite is sometimes one of the youngest minerals in the veins, as 
observed, for example, in the C. K. & N. vein, it is often altered to hollow 7 siliceous 
pseudomorphs and these in turn embedded in quartz. It was evidently formed 
at more than one period, as will be seen when the structure of the Howard flat vein 
is described, and in the Elkton mine (Walter vein) its relation to quartz carrying 
calaverite is such as to indicate that the celestite is the older mineral. Specimens 


176 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

from the El Paso mine, level 3, C. Iv. & N. vein, show that an original crust of 
celestite is converted into pseudomorphs of quartz coated by quartz crystals on 
which a still later generation of fluorite and lastly quartz is again deposited. 

At the Blue Bird mine a fissure filling of “purple quartz,” a fine-grained aggre¬ 
gate of quartz grains in which still smaller cubes of fluorite lie embedded, has been 
broken, and the new cementing material consists of various forms of quartz, chal¬ 
cedony, and opal, usually appearing as a yellowish or white flinty material. One 
specimen of this shows under the microscope a network of bars of cryptocrystalline 
silica, the interstices between which are filled by clear radial chalcedony, including 
a few grains of fluorite. Some of this silica bears evidence of being pseudomorphs 
after a doubtful mineral now dissolved. Replacement of dolomite is shown by 
specimens from the Orpha May dump. Quartz crusts are here covered by small 
pyrite crystals and sharply defined primary rhomboliedrons of dolomite, all of 
which are coated by a yellow fiber of opal, in most cases forming a thin, empty 
shell, the original mineral having been dissolved. Like the tellurides, however, 
celestite, on the whole, is particularly characteristic of the medial vuggy portions 
of the veins. Chalcedony and opal belong to a late stage of the vein formation 
and occur characteristically as films or botryoidal incrustations in the vugs. 

In the narrow veins and seams which cut through the altered rock near the 
fissures a very definite order of succession is often noted. Adularia in well-devel- 
oped crystals or crystalline aggregates is the first mineral deposited and coats the 
walls, while the interior of the vein is filled with granular quartz, in which as the 
latest product rhombohedrons of dolomite are contained (PI. XVII, B ). In latite- 
phonolite of the Findley mine the succession is adularia (oldest), dolomite with 
calaverite, fluorite, quartz (youngest); the surface of the quartz is dull and cor¬ 
roded. Wavellite is a primary vein mineral and in places forms tiny filled veinlets 
accompanied by pyrite. The walls of these veinlets are lined with adularia. 

To speak very broadly, the vein filling began by the deposition of adularia 
and the base sulphides, such as pyrite, sphalerite, and galena ; then followed deposits 
of quartz, fluorite, and dolomite, sometimes repeated, and toward the last tellurides 
and celestite, followed in some places by repeated deposition of quartz and fluorite. 
The closing chapter is in some veins represented by extensive deposition of quartz 
and chalcedony, frequently replacing the celestite and coating all other constitu¬ 
ents. Molybdenite is usually intergrown with pyrite and zinc blende, indicating 
that it is one of the older vein minerals. 

STRUCTURE. 

To a certain extent the larger structures of the lodes have been described in 
the section devoted to the fissures. The present section relates particularly to 
the modes in which the various minerals are arranged within individual fissures. 

The Cripple Creek veins are characterized in general by a vuggy structure. 
Some fissures are solidly filled with vein matter, but this, on the whole, is not common. 
Usually the walls of the fissures are covered with crystalline crusts which have 
grown together here and there along the medial plane of the vein, having numerous 
cavities lined with projecting crystals of quartz, fluorite, and other minerals. In 
most cases the crusts are comparatively thin and the vugs narrow. In some lodes 


STRUCTURE OF THE FISSURE FILLINGS. 


177 


the veinlets which contain the tellurides are no thicker than a sheet of paper, as 
may be seen in the Captain stopes in the Portland mine, in the northern part of 
the Mary McKinney mine, in the stopes in gneiss in the Midget and Abe Lincoln 
mine, and in many of the lodes in phonolite dikes. Even such minute fissures 
are not everywhere completely fdled. They are generally planes of easy fracture 
and their walls, when cleft apart, are seen to be covered with a thin drusy coating, 
consisting in most cases of quartz or fluorite, with crystals of calaverite. In the 
Captain stopes the drusy coating is usually dolomite. In the gneiss of the Abe 
Lincoln and Midget mines many of the gold-bearing fractures are so narrow as to 
be visible only by the aid of a lens. As a rule, each little fissure, however, is asso¬ 
ciated with a zone of metasomatic alteration in the gneiss, suggestive in its general 
appearance of the bands of greisen accompanying cassiterite veinlets, such as those 
of Geyer in Saxony. This zone is usually greenish, lacks the brilliant scales of 
biotite elsewhere abundant in the gneiss, and may be an inch or more wide. It is 
thus in most cases a more conspicuous feature than the fissure which it accom¬ 
panies. The veinlets themselves commonly consist of films of pyrite or quartz 
and tellurides, and many of them, as may be seen with a lens, are minutely vuggy. 

The majority of the individual veins in the district range from the width of 
those just described up to 5 or 6 inches, and the vugs have a corresponding range 
in size. The crustified minerals on the fissure walls grow outward somewhat 
unevenly, so that vugs occur irregularly in the veins instead of being uniformly 
arranged along the medial plane. Moreover, some parts of a vein may be solidly 
filled with tellurides and gangue, while other parts show merely thin crusts on the 
walls, as may be seen in the C. K. & N. vein and in some of the flat veins in the Mary 
McKinney mine. In some sheeted zones slabs of country rock became loosened 
when the fissures were opened. Subsequent deposition of vein minerals has cov¬ 
ered these detached fragments with crystalline coatings and cemented them at 
points of contact to the fissure walls, leaving vuggy spaces into which it is possible 
to thrust an arm. Some of the best examples of such gaping sheeted zones were 
seen in the C. K. & N. and Blue Bird mines. Where the Assuring is locally irregular, 
as in the pay shoot of the El Paso vein alongside the phonolite dike (see p. 351), the 
entire ore body may consist of a mass of rock fragments cemented together by 
little vuggy veinlets of quartz or other gangue mineral, carrying tellurides of gold. 
Where the shattering has been more intense and where more or less of the shattered 
rock has been removed in solution, each fragment may be surrounded by an envelope 
of quartz and fluorite, as in a curious expansion of the Elkton lode presently to be 
described. 

Although the vugs are usually small and often minute, a few veins in the dis¬ 
trict contain cavities of notable size. The Howard flat vein, where cut in the 
Ophelia tunnel, has vugs large enough for a man to crawl into, and lined with rough 
crystalline incrustations of quartz and fluorite. The crystals of these minerals 
have evidently in part grown around hollow siliceous pseudomorplis, probably after 
celestite. In one of the cross veins in the Last Dollar mine, on level 12, occurred a 
vug 12 feet long and 2 feet wide. Probably the largest and most remarkable 
cavity in the district was that on level 7 of the Elkton mine, whence issued the 


178 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


O' A"".-'-’<> .<7 o' ^ 

O-;. ' A - <>> A? A* 3 


water which in 1901 flooded the lower levels of the mine. This, as diagram- 
matically sketched in fig. 12, is a lateral offshoot from the Elkton lode at a point 
where the breccia had been locally shattered. Apparently the finer fragments 
were partly removed in solution, and the larger ones and the walls of the irregular 
cavity were coated with crystals of quartz and fluorite, which in part were accom¬ 
panied by tellurides. In this case the fluorite is not merely a coating on the frag¬ 
ments which partly filled the cavity, but has to some extent metasomatically 
replaced them. 

The crystalline crusts which coat the walls of the fissures seldom show well- 
defined continuous banding such as is often found in crustified veins of greater 
width and of more abundant filling. ‘ The development of such a structure requires 
a fairly definite mineralogical sequence or paragenesis and fissures of greater average 
width than those of Cripple Creek, so that the crusts as successively deposited will 
be thick enough and continuous enough to be distinctive in spite of minor irregu¬ 
larities of crystal growth. Fairly regular banding was noted, however, in the 

Galena mine, the order of crys¬ 
tallization being (1) quartz, ga¬ 
lena, and sphalerite; (2) radial 
pyrite; (3) sphalerite; and (4) 
fluorite, rhodochrosite, and 
sphalerite. A rather indistinct 
banding of quartz and fluorite 
was observed also in t he C. K. & N. 
vein, on level 4 of the El Paso 
mine. The Mary McKinney lode 
is apt to show a sharply defined 
filled central vein. A specimen 
of one-half of the vein, 3 inches 
in thickness, shows that the dep¬ 
osition began by two narrow 
fluorite bands separated by a 
narrow quartz seam. On top of the second fluorite band calaverite crystals are 
deposited; then follow mixed quartz and fluorite coated by thin, yellow opal and 
cryptocrystalline chalcedon}^. 

The Gold Coin vein, on level 12, shows distinct banding. Next the wall is 
deposited quartz with pyrite, zinc blende, and galena; then follows 3 mm. of solid 
comb quartz covered by a drusy mass of crystallized quartz and fluorite. Idle 
Puzzle vein in a similar manner shows crusts about 1 inch thick, consisting of zinc 
blende and galena covered by a quartz crust on which slender crystals of calaverite 



HE* 

v<? o. <:=■■ ' c 

fSSsliSi 

V/.Breccia .■<?\ 

• ?-<j gv 

; ' : .Q 4(a\ 

•A• o •, • y,1 <3 4 , a 

Fig. 12.—Sketch section across expansion of vein on level 7, Elkton 
mine, looking north 


appear. 

In general, then, the typical vein of Cripple Creek consists of one or more 
fissures ranging from 1 to 6 inches in width, whose walls are lined with crystalline 
crusts of quartz, fluorite, or dolomite. Along parts of the vein the crusts are thick 
enough to meet and the vein is solidly filled with tellurides and gangue, but in most 
parts the medial line of the vein is open or vuggy, and the crystals of calaverite or 
sylvanite project with crystals of the gangue minerals into the vugs. In many 














STRUCTURE OF THE FISSURE FILLINGS. 


179 


veins the tellurides are practically confined to the vugs, and this is certainly their 
most characteristic occurrence; but in a few cases they are embedded in the compact 
or solid portion of the vein as well. 

There are numerous variations from what may be regarded as the typical vein. 
Some fissures are completely filled with granular pyrite, as in some of the seams 
of the Doctor-Jackpot lode; some with a crumbling mass of pyrite and fluorite, as 
a vein exposed in the Granite mine, on level 6, north of the shaft; some with a 
hard, fine-grained, dark-purple aggregate of quartz and fluorite, as parts of the Blue 
Bird, Buena Vista, Doctor-Jackpot, and Work veins, and a cross vein in the Findley 
mine, which is in places 15 inches wide. Such fissure fillings, however, are seldom 
productive. Some fissures, like the Howard fiat vein, are in some places much 
wider than the typical veins; but although much ore has come from the Howard 
vein, it has not been obtained from the exceptionally wide and vuggy portions. 
Some fissures, like parts of the Gold Coin and Mary McKinney veins, were originally 
filled with brecciated rock derived from their walls. This crushed material was in 
part cemented and in part metasomatically replaced by gangue minerals and ore. 
The Bobtail vein of the Portland mine is also a mineralized breccia-filled fissure. 
In this case, however, the breccia does not seem to have been derived from the 
walls of the fissure. 

The filling of the Pointer vein, which is in places 2 or 3 inches wide, has 
a peculiar cellular structure, the cavities being lined with small crystals of quartz 
and fluorite. The structure is due in part to the filling of fissures in a sheeted 
zone and in part to a combination of metasomatic replacement and solution of the 
thin slabs of rock between the fissures. 

As regards minor structural details, the veins present few features worthy of 
note. The vein quartz, when seen in thin section under the microscope, rarely if 
ever shows such optical homogeneity as is characteristic of the quartz of the 
Mesozoic gold veins of the Pacific coast. The Cripple Creek quartz has a wavy 
extinction between crossed nicols and shows a pronounced radial optical structure, 
as if each crystal grain were composed of submicroscopic radial fibers. The struc¬ 
ture is suggestive of chalcedony, but is more shadowy, with less regularity and 
sharpness of definition of the constituent fibers. A similar structure is common 
in the quartz of the San Juan region, Colorado. While having some resemblance 
to the well-known strain phenomena produced in crystals by pressure, the structure 
here described can scarcely be explained as a result of strain. The structure is 
particularly well shown in quartz crystals projecting into vugs, as in the Howard 
flat vein, and although the vugs may have been filled with liquid under pressure, 
such hydrostatic pressure could hardly produce strain phenomena. In the Gold 
Coin vein crystals of quartz with this radial optical structure are incrusted with 
chalcedony. The boundary between the two minerals is not sharp, and there 
seems to have been no break between the deposition of quartz and that of 
chalcedony. This suggests that the structure of the optically anomalous quartz 
is also minutely fibrous and in no way due to pressure upon a formed or partially 
formed crystal. It is noted that a lack of optical homogeneity is characteristic 
also of the adularia crystals that project into the vugs of the ore metasomatically 
deposited in the Pikes Peak granite. 


PLATE XVII. 

Photomicrographs of Ores. 

A. “Purple quartz” (8 C. C.), Morning Glory mine, 750-foot level, Doctor vein. Liglit-gray cubes=fluorite. 

White cementing mass=microgranular quartz. Black=pyrite. Magnified 28 diameters. 

B. Filled veinlet in altered latite-phonolite (680 C. C.), Last DoUar mine, level 11. ^=granular quartz; 

/=fluorite; d=dolomite; a=adularia. Magnified 28 diameters. 

C. Quartz from Howard flat vein, Ophelia tunnel (648 C. C.), deposited on celestite and replacing this mineral. 

Crossed nicols showing radial structure and variation of grain. Magnified 28 diameters. 

D. Altered latite-phonolite, level 12, Last Dollar mine, showing pyroxene crystal replaced by pyrite, dolomite, 

and fluorite. Black=pyrite. Magnified 28 diameters. 

E. Altered latite-phonolite (452 C. C.), Last Dollar mine, showing titanite crystals altered to rutile, calcite, 

and quartz. Black around periphery=rutile. Light center=quartz and calcite. Magnified 40 
diameters. 


180 


U. S. GEOLOGICAL SURVEY 


PROFESSIONAL PAPER NO. 54 PL. XVII 



E 


PHOTOMICROGRAPHS OF ORES. 







STRUCTURE OF THE FISSURE FILLINGS. 


181 


The quartz is apt to vary considerably in texture in a single specimen, ranging 
from rock of fine grain, but with still distinctly visible partly idiomorphic individ¬ 
uals, to rather coarse vein quartz (PI. XVII, C ). The pyrite crystals are usually 
inclosed in quartz; rarely in fluorite. 

Fluid inclusions are abundant and often show moving bubbles which do not 
disappear or change form upon heating to +35° C. and above. The fluid is, there¬ 
fore, in all probability an aqueous solution. The inclusions are apt to have 
extremely irregular forms and often contain some solid material besides the fluid 
and the bubble, but this material is not crystallized; it forms irregular masses and 
adhesion to the walls. 

The so-called “purple quartz” or “massive fluorite” of some of the veins is 
usually a mixture of quartz, fluorite, and dolomite in various proportions. It is 
deep purple and has a fine, evenly granular texture. 

The microscope shows that the dominant mineral is 
generally quartz in allotriomorphic grains. In¬ 
cluded in the quartz are small cubes of fluorite 
and in many cases rhombohedrons of dolomite 
(PI. XVII, A). The fluorite, as is usual in the 
darker varieties of this mineral, is very unevenly 
colored, the deep-purple pigment occurring in little 
flecks here and there in the cubes. On the whole, 
thin sections show much less purple than the deep 
color of the material, as seen in masses, would sug¬ 
gest. In most cases the quartz-fluorite aggregate 
is purely a fissure filling. In the Elkton mine, how¬ 
ever, on level 7, granular fluorite with some quartz 
has metasomatically replaced breccia. Thin sec¬ 
tions of this material show the same uneven colora¬ 
tion, the most deeply colored cubes or grains being 
those which are in contact with the breccia along 
the irregular surface of replacement. At a little 
distance from this contact the fluorite as seen in 
thin section is nearly colorless. This suggests that 
the fluorite grains may in some cases naturally lose 
their deep color which presumably is due to included 
organic material. 

A rather unusual vein filling was noted at one 
point in the C. Iv. & N. vein. The principal fissure 
is here an inch wide and for the most part is only 
partly filled with vuggy quartz and calaverite. At 
one place, however, the vein is filled with a fine-grained dark-gray mass about 3 
inches long, which appears to have been originally a fragment of rock wedged 
•into the fissure. This fragment has been metasomatically altered to an aggregate 
of quartz and minute crystals of pyrite, with here and there a speck of calaverite. 
Tn crusting the ends of the fragment and the walls of the fissure is a layer of quartz 
and calaverite of varying width. Coating this and almost enveloping some of the 



Fig. 13.—Local structure in C. Iv. & N. vein. 
Walls consist of reddish granite containing 
pyrite in cracks perpendicular to vein. In¬ 
closed fragment of altered rock in open fis¬ 
sure and crusted by calaverite and quartz 
covered by radial pyrite. On top of the 
latter comb quartz. 1. Fragment of altered 
rock wedged in fissure. 2. Minutely fis¬ 
sured granite with pyrite. 3. Calaverite. 
4. Earlier generation of quartz. 5. Radial 
pyrite. 6. Later generation of quartz. 







182 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

calaverite crystals is a layer of radial pyrite with a minutely botryoidal surface. 
This layer in turn is incrusted by comb quartz containing some calaverite. The 
structure of this ore is shown somewhat diagrammatically in fig. 13. 

The occurrence of hollow, acicular, or prismatic pseudomorphs, which are 
probably in all cases formed by the incrustation of celestite by a shell of drusy 
quartz and the subsequent solution and removal of the strontium sulphate, fre¬ 
quently gives a characteristic structure to the vein fillings. Sometimes these 
pseudomorphs, which are usually opaque and are milk white or yellow, are com¬ 
pletely embedded in the quartz or, less commonly, in fluorite. In most cases, 
however, they project into the vugs, and with their incrusting quartz crystals 
form a particularly rough crystalline lining, as may be well seen in the Howard 
flat vein in the Ophelia tunnel. The original celestite crystals, as shown by the 
pseudomorphs and by the crystals seen in the C. K. & X. vein, are slender needles, 
usually of rhombic cross section and tapering to a point. In the Howard flat vein 
such needles have been radially incrusted with quartz crystals so as to form little 
stalactites with diameters ten to twenty times that of the original celestite needle, 
and with lengths of 1 or 2 inches. On these stalactites were implanted a second 
generation of celestite crystals which have in turn been incrusted with quartz and 
dissolved away. Some of the pseudomorphs which showed a hollow central canal 
partly filled with a white earthy substance were analyzed by Mr. George Steiger, 
who found that they contained 2.04 per cent BaO, 0.04 per cent SrO, 0.06 per cent 
CaO, and an amount of S0 3 which probably would suffice to form sulphates in 
combination with the bases. It is possible that the original mineral was barite, 
but the crystal form rather points to celestite with a small percentage of baryta. 
During the pseudoinorphic action the more soluble sulphates of strontia woidd be 
carried away, leaving a residual of not easily soluble barite. Some of the hollow 
pseudomorphs found in the ores have cross sections that are sharply rectangular 
instead of rhombic. Such pseudomorphs were observed in the Golden Cycle mine 
and, embedded in chalcedony, in the Blue Bird mine. The original mineral after 
which these shells are pseudomorphs has not been ascertained. It may have been 
celestite of a different crystal habit from that characterizing the known occurrences 
of this mineral in the district. 

EXCEPTIONAL VARIETIES OF VEINS. 

LEAD-ZINC VEINS. 

Narrow veins with quartz gangue, predominating galena or zinc blende, and 
subordinate telluride occur along the western side of the district from Poverty 
Gulch down to Squaw Gulch and the vicinity of the Pointer and Puzzle mines. 
The strike is usually northeasterly. No strict line separates these veins from the 
normal telluride veins. Where there is much galena some silver is present, but 
the high silver values are, as a rule, connected with the occurrence of tetrahedrite. 
Many of the galena veins are close to normal telluride veins. 


EXCEPTIONAL VARIETIES OF VEINS. 


183 


CELESTITE VEIN. 

The only occurrence of a celestite vein was found in level 7 of the Ironclad mine, 
where the crosscut to the main vein intersects a massive vein about 1 foot wide 
and striking northeasterly. The vein, which is poor in gold, but is said to carry 
some lead, contains streaks of limonite and clay, but consists chiefly of white 
granular celestite, coated with chalky crusts of a hydrous sulphate of strontia. 

BIOTIT E-FELD SPAR VEIN. 

A biotite-feldspar vein, the only one of this very remarkable type, was found 
in the Ophelia tunnel, about G,000 feet from the portal, in the Dolly Yarden 
claim. Penrose® mentions a possible similar occurrence on the Ocean Wave 
claim, which coidd not be definitely located, but gives no details. The vein, which 
crosses the tunnel with a general northerly direction, appears as a zone oi narrow 
but well-defined stringers, the aggregate thickness of which is 6 to 10 feet. They 
consist of white drusy feldspar ; pyrite, partly with crystal outlines, and black 
biotite, the latter in well-crystallized hexagonal prisms. All three minerals are 
intimately intergrown; pyrite and small foils of biotite are disseminated for some 
distance into the surrounding rock, which is sharply separated from the vein filling. 
The feldspar consists of coarsely granular orthoclase with narrow intergrown 
lamellae of albite. An analysis of the feldspar by Mr. George Steiger yielded 13.27 
per cent Iv 2 0, 1.36 per cent Na 2 0, and 0.04 per cent CaO. The biotite lies embedded 
in the feldspar as large ragged foils of pale yellowish-brown color and wide axial 
angle. The pyrite contains only 0.08 ounce of gold and 0.20 ounce of silver per 
ton. The whole occurrence is very unusual. The type of the feldspar with albite 
lamellae is granitic and has not before been observed in distinct veins, to which 
class this deposit undoubtedly belongs. It is not an altered granitic dike. It is 
so entirely different from the other types of deposits in the district that it must 
have been formed under unusual conditions, probably at a greater degree of heat 
than prevailed during the principal vein-forming epoch. 


a Sixteenth Ann. Rept. U. S. Geol. Survey, pt. 2, 1895, p. 129. 





CHAPTER IX— PROCESSES OF ALTERATION. 


METASOMATISM IX CONNECTION WITH VEIN FORMATION. 

EXTENT OF ALTERATION. 

The volcanic rocks of Cripple Creek have been extensively altered, so much so 
that in places it is impossible to obtain entirely fresh specimens. This alteration 
may be traced to three causes—vein formation, ordinary hydrometamorphism, 
and direct oxidation. The first of these is-not now operative, while the two latter 
processes are still actively engaged and are apt to superimpose their effects on the 
alteration due to vein formation. The more important of these two is oxidation, 
which is described in detail on pages 196 to 204. Ordinary hydrometamorphism 
producing chlorite, serpentine, sericite, etc., is caused by surface waters below the 
zone of oxidation. Its changes are not very far-reaching and only in very few 
cases has it radically altered the mineralogical composition of the rocks. 

To processes of vein formation may unhesitatingly be referred the greater part 
of the alteration below the reach of oxidizing waters. All rocks have been affected, 
the breccia most of all in consequence of its porous and permeable character. There 
are, in fact, comparatively few places where the breccia retains its original appearance. 
Latite-phonolite and syenite have yielded less readily to alteration, and fresh spec¬ 
imens maybe obtained from all of the bodies mapped. Phonolite and basalt dikes, 
especially the latter, are usually more or less affected, while the larger outlying 
phonolite masses are, in most cases, practical^ fresh. The Beacon Hill phonolite 
has suffered much more than the ring of phonolite intrusions which, contained in 
granite, surround the central breccia. Granite, schist, and gneiss are only locally 
altered near the breccia contact or near veins traversing them. 

CHARACTER OF ALTERATION. 

On the whole, and compared to similar changes in other districts, the alteration 
of the Cripple Creek rocks is remarkably slight. It is elsewhere not uncommon 
near gold-quartz veins to find diorites, amphibolites, or diabases completely changed 
to white, soft rocks chiefly composed of sericite, quartz, and carbonates. Here, 
on the contrary, alteration very rarely obliterates the original character of the rock 
as seen under the microscope or in specimen. The minerals formed are pyrite, asso¬ 
ciated occasionally, but not commonly, with a little zinc blende or galena, further 
sericite, adularia, dolomite, fluorite, and quartz; the latter is wholly subordinate and 
forms only under certain exceptional conditions, resulting in complete replacement 
of the rock by quartz and pyrite. Sometimes apatite also forms. Besides sericite, 
roscoelite (a yellowish-green vanadium mica) and a light-green mica of doubtful 
composition are sometimes present, and rutile, with some calcite, develops from 
titanite. 


184 


METASOMATISM IN CONNECTION WITH VEIN FORMATION. 


185 


Chemically the process when carried to completion involves an almost entire 
loss of soda and a corresponding gain of potash attending the formation of sericite 
and adularia. Small amounts of sulphur, carbon dioxide, and fluorine are intro¬ 
duced. The percentage of silica is usually slightly reduced and a leaching of 
magnesia and lime is sometimes evident. After all, the most important process 
is the replacement of soda by potash, so commonly resulting elsewhere from the 
action of thermal waters at moderate temperature and pressure on ordinary feld- 
spathic rocks. 

METASOMATIC MINERALS. 

Among the metallic minerals pyrite is easily the most common, and develops 
abundantly by replacement as small crystals in the groundmass of the porphyritic 
rocks or in the cementing mass of the breccia, as well as in phenocrysts or in the 
minerals of granular, rocks. The form is usually that of the pyritohedron combined 
with the cube; some larger masses have irregular outlines. Although the mineral 
develops throughout the rock, it is most abundant near replaced phenocrysts of 
pyroxene, amphibole, or biotite; it also forms directly from magnetite, and on the 
whole the iron seems to be supplied by the original minerals of the rock, and the 
transformation is effected simply by the addition of sulphur derived from hydrogen 
sulphide or from sodium sulphide. 

Zinc blende appears occasionally in the altered rocks, but is, on the whole, 
very rare; it is associated with pyrite as anhedral grains of dark-brown color. 
Other sulphides are very seldom observed. 

Tellurides, chiefly calaverite, appear as metasomatic minerals in granite, schist, 
breccia, or phonolite, and also in the basic dikes. It forms anhedral grains, rarely 
prisms, and is associated with pyrite. Another form of its occurrence is as minute 
crystals coating small cavities of dissolution in various rocks, such as granite and 
phonolite. Compared to its abundant development as crusts in fissures, its meta¬ 
somatic distribution is very limited. 

Magnetite, specularite, pyroxenes, and amphiboles do not appear as metaso¬ 
matic minerals in these deposits, and are, in fact, unstable under the influence of 
these vein-forming agencies. Epidote is very rare, and probably also unstable 
under these conditions. 

Sericite is common, although the extensive sericitization seen in the wall rocks 
of many classes of veins is here absent. The mineral forms, to some extent, as 
small foils and fibers in orthoclase (PL XVIII, B ), though wholly sericitized crystals 
are very seldom encountered. Much more commonly it forms as minute fibers in 
the sodic silicates, such as nepheline, sodalite, and analcite, also in soda-lime feld¬ 
spars, and in pyroxenes, amphiboles, and brown micas. The yellowish-green vana¬ 
dium mica, roscoelite, is seen occasionally in granite (Ajax mine) or in breccia 
(Mary McKinney mine). 

As a first stage in common hydrometamorphism, as wqjl as in hydrothermal 
metamorphism, of biotite, amphibole, and pyroxene in gneisses, latite-phonolites, 
and similar rocks, a variety of mica is often noted which does not seem to correspond 
to any known variety. Its aggregates of small shreds and foils of deep grass-green 
to yellowish-green and brownish-green color have a noticeable though not very 
strong pleochroism and vivid colors of polarization. 


\ 


PLATE XVIII. 

Photomicrographs of Ores. 

A. Quartz veinlet with radial structure in breccia, Empire State mine, level 10; crossed nicols. Magnified 

28 diameters. 

B. Phenocrysts of orthoclase in latite-phonolite, Gold Sovereign mine, level 7, showing sericitization. Lighter 

central areas indicate abundant microcrystalline aggregates of seric.ite, while in the darker periph¬ 
eral spaces more feldspar remains. Black areas indicate pyrite. On veinlets and in small spaces 
of dissolution adularia has developed. Crossed nicols. Magnified 28 diameters. 

186 


\ 


U. S. GEOLOGICAL SURVEY 


PROFESSIONAL PAPER NO. 54 


PL. XVIII 




PHOTOMICROGRAPHS OF ORES, 








METASOMATISM IN CONNECTION WITH VEIN FORMATION. 


187 


Serpentine develops in places from ferromagnesian silicates under the influence 
of incipient vein action, but is probably soon altered to carbonates. 

Adularia is a pure potassium feldspar which occurs in some mineral veins. ° 
The Cripple Creek deposits contain a considerable amount of this mineral, both as 
fissure-filling and more prominently as a metasomatic product . b It nearly always 
shows crystallographic outlines, and as the forms are combinations of the prism 
and a dome, the outline of the crystals usually shows a rhombic, somewhat elon¬ 
gated form. Larger grains often have peculiar optical irregularities, somewhat like 
that of the quartz in the filled veins of Cripple Creek (p. 179), the mass being 
divided into several irregularly defined sections with slightly differing optical 
orientation. 

Adularia forms in all the various rocks, most abundantly, however, in the 
metasomatically altered granite, the so-called granite ore. In little veinlets its 
crystals coat the walls as they do in cavities of dissolution, where the central part 
is apt to consist of dolomite or fluorite with pyrite. In the mass of the rock it 
occurs as rhombic sections or is attached to old orthoclase crystals, as marginal 
growths with parallel orientation or healing fissures in the same. Sometimes the 
distinction from the primary orthoclase may be difficult, but the more recent min¬ 
eral is usually very clear and free from inclusions. In the granite much of the 
older feldspar is microcline, but the secondary mineral never belongs to this species. 
It is somewhat surprising to see sericite and adularia develop in the same rock, 
side by side (PI. XVIII, B ); in some instances, indeed, fibers of sericite are devel¬ 
oped in a mass of adularia. However, the principal part of the adularia is confined 
to the granite, while in the volcanic rocks sericite is more abundant. To a certain 
extent the formation of adularia is due to the prevalence of the orthoclase in the 
original rock, for, as pointed out by Van Hise, c the mineral species most abundantly 
present have the advantage over other kinds of minerals, which are absent or spar¬ 
ingly present, in determining the character and the orientation of new additions. 
Thus, quartz will develop most abundantly in siliceous rocks and orthoclase in 
those rich in that kind of feldspar. 

Quartz is formed during the alteration of sericite from orthoclase and during 
the decomposition of ferromagnesian silicates, but it appears to be carried away in 
soluble form. At any rate, quartz is not of general occurrence as a metasomatic 
product, though it is often deposited on fissures. Quartz crystals are seldom 
deposited in the small cavities of dissolution so common in the volcanic rocks. 
Adularia is far more common. Some occurrences of silicified rocks will be described 
below, but they occupy a rather exceptional position. 

Dolomite and calcite are common constituents of the altered rocks of all kinds. 
Dolomite replaces the cementing mass in breccia, the ferromagnesian silicates in 
latite-phonolites, and develops almost as easiH in the orthoclase. The dolomite 
always tends toward a crystalline development, the form being a more or less 
roughly outlined normal rhombohedron. Siderite develops from magnetite in small 
quantities. 

a Lindgren, W., Orthoclase as a gangue mineral in a fissure vein: Am. Jour. Sci., 4th ser., vol. 5. pp. 418-420. 
b Lindgren, W., Metasomatic processes in fissure veins: Trans. Am. Inst. Min. Eng., vol. 30, 1901, p. 612. 
c A treatise on metamorphism: Mon. U. S. Geol. Survey, vol. 47, 1904. p. 122. 



188 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


Fluorite is rarely ver} r abundant, but is widely distributed. It lias not the same 
tendency to crystallographic development as in the filled veins, but occurs in little 
masses filling small cavities of dissolution or replacing any one of the constituents 
of the rock. The color is always purple, frequently deepened in spots. 

Rutile forms easily from titanite; pseudomorphs of rutile, calcite, and chal¬ 
cedony after crystals of titanite are common in the latite-phonolites. 

METASOMATIC CHANGES IN PHONOLITE. 

The changes which have taken place are rarely very far-reaching. A phonolite 
dike, followed by the vein, on the 370-foot level in the C. K. & N mine shows small 
cavities of dissolution coated by quartz, pyrite, fluorite, and tellurides. Under 
the microscope the structure of the rock is seen to be perfectly preserved. The 
segirine-augite is replaced b}^ calcite and nests of serpentine; pyrite is abundant in 
small crystals, in many places probably replacing magnetite. There is very little 
sericite, and the orthoclase seems practically fresh. This phonolite is a low- 
grade ore. 

A fine-grained dike from level 10 of the Last Dollar mine, 100 feet south of 
the shaft, shows dolomite or calcite distributed throughout the rock; here also 
magnetite is converted to pyrite and siderite. Small pyrite crystals are abundant 
and veinlets of adularia, carbonates, pyrite, zinc blende, and galena traverse the 
rock; the adularia is the earliest mineral formed. This altered dike is not classed 
as ore. A light yellowish-gray phonolite from the Cheyenne vein on level 11 of 
the Isabella mine, 800 feet south of the Lee shaft, is a normal rock containing very 
little pyrite and some fluorite in irregular aggregates. The nepheline is converted 
to sericite, while the orthoclase appears unaltered. However, many of these rocks 
may contain much more adularia than is apparent. 

METASOMATIC CHANGES IN SYENITE. 

The normal sj^enite from the Last Dollar mine contains no carbonates and, 
sericite, green mica, and chlorite are only slightly developed. The magnetite is 
not altered. The rock along the vein at the north end of level 11 in the same 
mine is a syenite which has been subjected to unusually strong metasomatic action. 
It is bleached and softened and contains much pyrite, besides some black zinc 
blende and fluorite. The latter three minerals, with much quartz and adularia, 
form irregularly outlined replacement veins. Lmder the microscope the most 
abundant constituent is a granular orthoclase, while the ferromagnesian silicates 
and the magnetite have disappeared. Dolomite in anhedrons and rliombohedral 
forms mixed with a little sericite replaces this orthoclase abundantly. Sharply 
defined cubes and pyritohedrons of pyrite are plentiful, together with grains of 
black zinc blende. Rims of adularia sometimes surround the pyrite. Cavities of 
dissolution contain nests of quartz, adularia, and fluorspar; veinlets, probably 
chiefly formed bj" replacement, contain carbonates, quartz, and adularia, and in 
one place calaverite with tetraliedrite; tellurides do not, however, appear in 
the mass of the rock. 


PROCESSES OF ALTERATION. 


189 


METASOMATIC CHANGES IN LATITE-PHONOLITE. 

The altered phases of the latite-phonolites are best studied at the Golden 
Cycle and Vindicator mines. Pyrite and dolomite are the minerals most abundantly 
introduced, but the alteration is not always uniform, so that in some specimens 
either of these two minerals may be lacking. There is usually a development of 
sericite and adularia. 

The discussion may best begin by a description of the altered latite-phonolite 
of the dike along the Independence lode in Stratton’s Independence mine, collected 
in the Washington shaft by Cross. The analysis of the rock was made by W. F. 
Hillebrand in 1894, but has hitherto been unpublished. The rock is a yellowish-gray, 
fine-grained porphyritic latite-phonolite, with close relationship to the phonolites. 
There is a tendency to platy structure, emphasized by numerous small cavities of 
dissolution coated with crusts of fluorite, adularia, pyrite, and a soft material which 
seems to be a mixture of sericite and kaolin. Throughout the rock are small specks 
of fluorite and pyrite. Under the microscope the large phenocrysts of orthoclase 
are little altered; the groundmass consists of narrow laths of generally unaltered 
orthoclase, between which lies an interstitial mass of fine sericite fibers clearly 
replacing the analcite, sodalite, or nepheline which, in the fresh rocks, are apt to 
occupy this position. Small crystals of pyrite are distributed throughout. Spaces 
of dissolution are plentiful and are filled with adularia, while the central part is 
occupied by fluorite. In one place fibers of sericite project into the adularia. No 
biotite, amphibole, or pyroxene are visible, and these minerals have no doubt been 
thoroughly decomposed. Neither are there any carbonates in this rock, though 
other specimens of the same dike collected by us contain a considerable amount of 
these minerals replacing ferromagnesian silicates. 


Analyses of altered and fresh latite-phonolites. 
[Analysts, W. F. Hillebrand (A. and B), W. T. Schaller (C.).] 



A. 

B. 

c. 


A. 

B. ! c. 


56. 74 

59.38 

57.91 

P 2 Ch. 

.25 

.08 


20.30 

19. 47 

so 3 . 


.37 . 


1.06 

1.60 


Cl. 


7° 

FeO. . 

1.19 


F. 

Undeter- 


MgO . 

.23 

.36 

.33 


mined. 



S. 


1.12 

CaO. 

.57 

1.96 

.81 

MnO. 




None. 

.15 . 

Na 2 0. 

.62 

7.80 

. 45 

1 BaO. 






.19 

. 13 

K 2 0. 

13.30 

5.83 

13.35 

SrO. 






Trace. 

.03 . 

H 2 0- . 

.33 

.11 






Li 2 0. 

Trace. 

Trace. 

h 2 o+. 

1.15 

.69 


FeS 2 . 




4.65 


Ti0 2 . 

.58 

.58 









ZrD 2 . 

.07 

.10 





co 2 . 

. 66 


100.10 

100.05 . 









A. Altered latite-phonolite, Washington shaft, Stratton’s Independence mine. 

B. Fresh latite-phonolite, west slope Bull Cliff (Petrographic reference collection No. 624). 

C. Altered latite-phonolite, level 11, vein No. 3, Vindicator mine (Cripple Creek collection No. 687). 


13001— No. 54—06-14 
































































190 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


Under B is given, for comparison, an analysis of a latite-phonolite poor in lime, 
which probably best corresponds to the composition of the original rock of A. This 
is, of course, an assumption, but the chemical composition of the Cripple Creek rocks 
is so well known that it can not be far from the truth. There are no volcanic rocks 
known from the district in which potassium predominates in the manner shown by A. 
The principal change, then, consists in a transformation of sodic silicates to potassic 
(serieite and adularia), and in the introduction of sulphur and fluorine. There is 
probably a slight loss of silica and a gain of water, though the fresh rocks usually 
contain 1 or 2 per cent chemically combined water which may be applied to the 
formation of secondary serieite. There is also a loss of chlorine and sulphuric acid 
from sodalite and hauynite, and a loss of a part of the lime, while magnesia, iron 
baryta, and titania have remained about constant. 

The rocks from the Golden Cycle mine are not conspicuously altered, except for 
small and abundant sharply defined crystals of pyrite; sometimes they are slightly 
bleached. The pyroxene crystals are converted to serieite or carbonates, or both, 
but chlorite and serpentine are generally absent. Veinlets of adularia intersect 
the rocks. With the maximum of alteration perhaps 10 per cent of dolomite and 10 
per cent of serieite have developed in the rock. The orthoclase contains fibers 
of serieite along the cleavage planes and sometimes irregularly replacing dolomite; 
very rarely, however, is the entire crystal replaced. Magnetite alters into pyrite. 

In the latite-phonolite of the Vindicator, Last Dollar, American Eagle, and 
Gold Sovereign mines the alteration is along the same lines, although dolomitic 
carbonates with a decided tendency to crystallization are abundant and replace both 
feldspars and pyroxenes. The amount of new-formed minerals rarely exceeds 15 per 
cent. In the latite-phonolite from the Last Dollar mine it is again noted that the 
small sodalite crystals first become sericitized. Pyroxene is converted to dolomite, 
with a little fluorite, serpentine, and pyrite (PI. XVII, D ). The large rounded 
magnetite grains are surrounded by white rings of siderite and the remaining part is 
more or less completely converted to pyrite. Titanite alters into marginal rutile 
with centers of calcite and chalcedony (PI. XVII, E .) A latite-phonolite from the 
dump of the American Eagle shaft shows abundant cavities of dissolution Idled 
with adularia, pyrite, rutile, and serieite. In one case tufted serieite coats the walls 
of the rounded cavity, which is filled with adularia. 

A latite-phonolite from the 1,300-foot level of the mine is a greenish-gray rock 
with crusted veinlets of liglit-greenish dolomite containing calaverite; this is sur¬ 
mounted by fluorite crystals covered again by clear hyalitic silica. The metasomatic 
alteration is slight. Pyroxene crystals are converted to serpentine and chlorite 
with magnetite, and the latter, near the veinlets, alters to pyrite. Crystals of 
pyrite are distributed through the ground mass and serieite and adularia develop 
in the orthoclase, the adularia usually filling cavities of dissolution. 

Another specimen from a very wide and rich part of No. 3 vein in the Vindi¬ 
cator mine, on level 11, is a greenish-gray latite-phonolite, in which some orthoclase 
crystals are visible. It contains much finely divided pyrite and seams of molyb¬ 
denite and calaverite. While the seams are rich, the rock between them is considered 
as barren. The microscope shows a large amount of orthoclase, both as phenocrysts 
and microliths in the groundmass. Serieite and carbonate occur in moderate quantity 


PROCESSES OF ALTERATION. 


191 


as very fine-grained aggregates. 


Analysis C on page 189 maybe calculated as follows: 
Si0 2 , 57.91; CaC0 3 , 1.50; MgO, 0.33; FeS,, 2.10; Na 2 0, 0.45; K 2 0, 13.35. Com¬ 
pared with analysis B it shows practically the same chemical result as analysis A. 
The great predominance of K.,0 can not be explained simply by the formation of 
sericite, but the rock must contain an abundance of adularia. 


METASOMATIC CHANGES IN BRECCIA. 

The volcanic breccia is far more extensively altered than any of the rocks thus 
far described. Its great porosity, often equivalent to that of a sandstone, fully 
explains this; the various chemically active solutions easily penetrated this rock 
by diffusion and convection. In the central part of the district, where fissures are 
abundant, as on Raven Hill and Gold Hill, it would be very difficult to find any 
entirely unaltered breccia. On the northern slope of Bull Cliff and on Big Bull 
Mountain, where there are few mineral deposits, much of the breccia is practically 
unchanged, except for a consolidation and hardening which in any rock of this kind 
involves some chemical processes. Such breccia is free from pyrite and appears 
as a purplish to brownish rock, the individual fragments of phonolitic rock being 
clearly visible. Unaltered breccia also occurs to the southwest of the Golden Cycle 
mine in a long crosscut ; here it is loose and sandy. Crosscuts north from the Vindi¬ 
cator and Isabella mines also run into unaltered breccia. In some kinds the angular 
fragments are several inches in diameter, while other breccias are very fine grained— 
in fact, look rather like unstratified tuffs. Granitic fragments of all sizes are 
plentiful at almost all places, but are naturally most abundant near the granite 
contacts. The altered breccia is a hard, bluish-gray or greenish-gray rock in which 
the individual fragments are sometimes difficult to observe. The most general 
change appears in the destruction of the dark silicates and their replacement by 
sericite, carbonates, and pyrite. Often a little residual serpentine is also seen. 
Pyrite is the commonest metasomatic mineral, and occurs widely distributed as 
very small crystals. The next mineral in point of abundance is a dolomitic carbonate 
sometimes also calcite, which replaces the cementing groundmass or any of the 
fragments and often shows roughlv rhomboliedral forms. Sericite in moderate 
quantities and some adularia appear in most altered breccias; the former partly, 
very rarely' wholly, replacing the feldspars or the cement, the latter preferring the 
veinlets or the cavities of dissolution. Anhedral fluorite appears in sporadic develop¬ 
ment replacing groundmass, and sometimes contains inclusions of carbonates and 
secondary apatite (specimens 708, 709 C. C.). The porous cement of the breccias 
sometimes allows zinc blende and molybdenite to be deposited with pyrite. Calave- 
rite also is known as a metasomatic mineral, for example, in the cement of a phonolite 
breccia from the W. P. H. mine, where it appears as irregular, soft, silvery-white 
grains. On the whole, the changes are entirety similar to those described in la tit e- 
phonolite. 

A breccia from the Golden Cyxle mine within the sheeted zone of the Legal 
Tender vein, between levels 8 and 9, is gray, hard, and fine grained, with abundant 
small and angular fragments of phonolitic rocks, in which the ortlioclase microlitlis 
are almost the only remaining original constituents. There are also many small 
pieces of granitic feldspars and a cement of the same character as the fragments. 


192 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


Small crystals of pyrite are distributed throughout the cement and the fragments, 
and carbonates have also developed abundantly in both. There is a moderate 
amount of very fine aggregates of sericite. No secondary adularia could be detected. 


Partial analysis of altered breccia from the Golden Cycle mine. 
[W. T. Schaller, analyst.] 

Iv 2 0. 

2.79 CO, 

1.06 
3.85 


Si0 2 .. 54.57 

CaO. 

MgO. 

Na 2 0. 


S (total). 


7. 50 
3.42 
1.29 


This may be recalculated to Si0 2 , 54.57; CaC0 3 , 4.97; MgC0 3 , 2.23; FeC0 3 , 
0.17; FeS 2 , 2.42; Na 2 0, 3.85; Iv,0, 7.50, and shows that, though the substitution of 
K,0 for Na 2 0 has not been complete, the rock contains much more potash than 
would be expected from its intermediate position between the composition of a 
granite and a plionolitic rock. At the same time, there is as much pyrite and much 
more carbonates than in the altered latite-phonolite described from the Vindicator 
mine (p. 190). Some silica has been removed, while probably very little lime has been 
lost. 

METASOMATIC CHANGES IN SCHIST AND GNEISS. 


The gneiss is generally unaffected by hydrothermal metamorphism, but adjacent 
to veins some changes are often observed, as is well shown in specimens from the Abe 
Lincoln mine, consisting of a reddish gneiss with narrow seams coated by quartz 
combs and a little pyrite and calaverite. These seams are surrounded by a greenish 
bleached zone 1 or 2 inches wide, containing disseminated pyrite and looking almost 
as if it contained epidote. 

Under the microscope the veinlets show much adularia, chiefly deposited along 
the walls and covered by quartz. In the rock itself, which is originally composed of 
quartz, orthoclase, and biotite, the latter mineral is the only one which has suffered 
extensive alteration, though the orthoclase contains some disseminated sericite. 
The biotite is transformed to dolomite with much crystallized pyrite and some of the 
peculiar light-green mica described on page 77. The latter gives the peculiar yel- 
lowisli-green color to the rock. A little adularia, often with crystal form, is also 
present and in places it appears to replace biotite, a fact also observed in the granite 
ore. In the Bonanza King lode of the Midget mine pyrite, galena, and zinc blende 
sometimes replace fissured gneiss. Schist fragments occurring in breccia in the 
W. P. II. mine consist of quartz, sillimanite, muscovite, and magnetite. The only 
alteration observed is that the original magnetite is changed into pyrite and that 
irregular grains of calaverite have developed. 

METASOMATIC CHANGES IN BASIC DIKES. 

% 

The various dark-colored basic dikes classified as monchiquites, vogesites, and 
trachydolerites are rarely seen in fresh condition, but are apt to form soft, greenish 
gray sheets in which the products of common hydrometamorphism and hydrothermal 
metamorphism may be superimposed. Calcite develops very abundantly, especially 
along the platy structure so often seen, but this is a common thing in dikes of 
tills character and has not necessarily any connection with vein-forming agencies. 
Zeolites also form in many places, as do serpentine, epidote, talc, and iddingsite. 










PROCESSES OF ALTERATION. 


193 


When mineralized the basic dikes become filled with minute crystals of pyrite 
and traversed by veinlets of quartz and calaverite. Sometimes calaverite forms 
metasomatically in the altered basalt. Specks and also larger bunches of galena and 
zinc blende develop in the basic dike of the Conundrum mine. 

A peculiar variety of metasomatic alteration has affected portions of the princi¬ 
pal basic dike in the Elkton mine, south of the main shaft. The altered rock is light 
gray, porous, and tliickly sprinkled with minute crystals of pyrite. The porosity is 
due to numerous little cavities of dissolution which are lined with small white crystals. 
Similar crystals coat the walls of the irregular seams traversing the rock. The 
material of the dike shows no trace of its original structure and is evidently much 
altered. 

The microscope shows that the dike has been locally changed to an aggregate of 
adularia, apatite, pyrite, sericite, and probably some calaverite. The apatite, 
which is remarkably abundant, is in slender greenish-white prisms of an entirely 
different habit from the stout smoky crystals characteristic of thfe latite-phonolite. 
The drusy crystals coating the pores and seams in the rock arc adularia. No chem¬ 
ical analysis has been made of this material, but there has clearly been a considerable 
addition of potash sulphur and phosphoric acid to the original dike rock. 

METASOMATIC CHANGES IN GRANITE. 

The Pikes Peak granite, along the breccia contact from the Elkton to Stratton’s 
Independence mine, is a reddish coarse-grained rock, noticeably deficient in dark 
constituents and frequently poor in quartz. It consists chiefly of microcline, some 
individuals of which are noticeably larger than the rest and give the rock a semipor- 
phyritic appearance; besides microcline, some quartz, oligoclase, microperthite, 
orthoclase, and biotite are present, the latter often chloritized and containing a little 
magnetite and epidote. A typical analysis of the Pikes Peak granite contains SiO,, 
77.03 per cent; MgO, 0.04 per cent; CaO, 0.80 per cent; Na 2 0, 3.21 per cent; K 2 0, 
4.92 per cent, but in the locality mentioned the amount of quartz is often smaller 
than would be indicated by the figures given, and the rock is rather a quartz-syenite, 
ranging over to a normal syenite, as shown by analysis A in the table on page 194. 

Near lodes this granite is often subject to marked metasomatic change; the 
reddish color changes to a light gray; the rock contains disseminated pyrite, sphal¬ 
erite, fluorite, and tellurides and becomes very noticeably drusy and honeycombed, 
the vugs being coated with the minerals just indicated. This is the so-called granite 
ore, which is of great economic importance in the part of the district outlined above. 
Penrose* noticed this ore, especially from Stratton’s Independence mine, but 
assumed that the change involved consisted of the dissolution of quartz, leaving a 
porous mass of feldspar. The characteristic feature of this mode of alteration b is, 
however, the abundant solution of orthoclase and microcline and reprecipitation as 
typical adularia. The quartz grains are also attacked and newly formed quartz 
deposited together with adularia. The biotite is the first mineral to be replaced by 
various other minerals, among them pyrite, calcite or dolomite, fluorite, adularia, 

a Sixteenth Ann. Rept. U. S. Geol. Survey, pt. 2, 1895, p. 201. 

b First described by Lindgren, W., Metasomatic processes in fissure veins: Trans. Am. Inst. Min. Eng., vol. 30, 1901, 
p. 650. 


* 





194 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


and roscoelite. Small pentagonal crystals of pyrite, as well as sphalerite, develop 
throughout the rock also; strings of these pyrite crystals joined by a thin sheet of 
quartz in some places penetrating the orthoclase. Light-colored sphalerite, inti¬ 
mately mixed with galena, occurs replacing orthoclase in ore from the Ajax mine. 
Small replacement veinlets as well as filled veinlets of adularia, quartz, and fluorite 
penetrate the rock and abundant irregular cavities of dissolution are coated with the 
same mineral associated with calaverite in well-crystallized form. 

The secondary adularia is often deposited in optical continuity about the 
remains of original feldspars. Sericite occurs in shreds in the orthoclase, but forms 
no important part of the rock. When granular quartz is developed it often possesses 
the optical “flamboyant” structure characteristic of Cripple Creek vein quartz. 
Apatite remains unaltered. Particularly large masses of granite ore were mined at 
the Ajax mine and two specimens of closely contiguous altered and unaltered granite 
from this mine were analyzed. 

Specimen 345 C. C., the analysis of which is shown under A in the table below, is 
a syenitic modification of the normal granite. It contains in the order of abundance, 
microcline, oligoclase, quartz, biotite, magnetite, apatite, and zircon. The oligoclase 
shows slight sericitization. The biotite is fresh. 

Specimen 344 C. C. (analysis B), taken at a distance of 1 foot from 345, shows 
much of the original microcline and quartz, although newly formed adularia is also 
abundantly present. Pyrite is disseminated throughout the rock, but also forms by 
replacement of original magnetite: The oligoclase is partly sericitized, and the 
biotite is transformed into aggregates of pyrite, fluorite, adularia, and a yellowish- 
green mica, which, without much doubt, is roscoelite. A small quantity of calcite or 
an allied carbonate appears as nests in the microcline. 


Analyses of fresh and altered granitic rock. 
[Analyst, W. F. Hillebrand.] 



A. 

B. 


Si0 2 . 

. 66.20 

59.58 

S0 3 ... 

AljOs. 

. 14.33 

16.00 

Cl. 


. 2.09 

.30 

F. 

FeO. 

. 1.93 

.65 


MgO. 

. .89 

.03 

MnO. 

CaO. 

. 1.39 

2.03 

BaO. 


. 2.58 

.98 

SrO. 

k 2 o. 

. 7.31 ' 

11.93 

Li 2 0. 

h 2 o-. 

. ,4S 

.32 

V 2 0 3 . 

H 2 0+. 

. .83 

.81 

MoOs.. 

Ti0 2 . 

. .65 

.75 


ZrO. 

.02 | 

(?) 

Less O. 

co 2 ... 

. .36 

.26 


P 2 Oo. 

. .25 

.32 



a 1.42 CaF. 

A (345 C. C.). Ajax mine, level 6. 

B (344 C. C.). Ajax mine, level 6, 1 foot from 345. 


6 2.55 S. 


A. 

None. 

Trace. 

(?) 

.12 

.13 

.18 

Trace. 

Trace. 


99.74 


B. 


None. 

(?) 

a. 69 
6 4.78 
Trace. 
.11 
.01 
Trace. 
.39 
.01 


99.95 

.29 


99.66 














































SEQUENCE OF PROCESSES OF ALTERATION. 


195 


The changes, as far as can be ascertained by a comparison of the analyses, involve 
a great loss of soda, which is more than compensated by an increase of over 4 per 
cent of potash. This corresponds to the development of soda-free adularia instead 
of sodic microcline and to the formation of sericite in the oljgoclase. There is a 
distinct decrease of silica, which is probably carried away in soluble form. Magnesia 
is practically eliminated, while lime is slightly increased. Whether any actual 
addition has taken place is doubtful. Fluorine, vanadium, and molybdenum have 
been introduced. The iron remains constant, substantiating the statement made 
above that pyrite forms principally from the constituents of the rock. Little 
change is noted in titanium and phosphorus. 

SILICIFICATION AND COMPLETE REPLACEMENT. 

A silicification of the rocks along the veins is exceptional. It does not extend far 
from the vein, and is probably developed only in case of very porous or shattered 
rocks. 

In several mines, and often associated with rich ore, occur small quantities of a 
dark, almost black, fine-grained and hard-vein material, which consists chiefly of 
quartz and pyrite, and which is probably due to replacement of detrital material or 
mud in which siliceous solutions could freely circulate. A drusy material of this 
kind from level 3 of the Isabella mine, 100 feet north of the Lee shaft, contains 
fine-grained quartz, with a little fluorite and abundant aggregates of pyrite, zinc 
blende, and molybdenite, as well as granular dolomite. A narrow, flat vein of this 
kind in an ore shoot on level 6 of the Abe Lincoln mine, in which gneiss is the pre¬ 
vailing country rock, consists of a granular mixture of quartz and idiomorphic 
adularia, abundant pyrite, grains of carbonate associated with felted nests of 
serpentine and sericite. 

SEQUENCE OF PROCESSES. 

The changes which have taken place in the rocks may be divided into those 
which are clearly and unquestionably caused by vein formation, as indicated by 
their occurrence along the lines of the mineralized fractures, and those affecting 
larger areas and less obviously produced by the solutions circulating on these 
fissures. Both Cross and Penrose® came to the conclusion that there were two or 
more epochs of alteration by hot waters and possibly also epochs of fumarole action 
by sulphuric acid, chlorine, and fluorine contained in the magma. They agree that 
the fissures and sheeted zones in the breccia could not have been produced in the 
soft and unconsolidated rock, and that, therefore, the general cementation and alter¬ 
ation of the breccia involving the formation of pyrite and sericite took place before 
the veins were formed. 

Although this view has some supporting evidence, we can not fully subscribe to 
it. It is true that hot waters circulated through the volcanic rocks for a considerable 
period and that the solutions varied from time to time. Almost immediately after 
the explosive action had ceased the breccia must have been permeated by steam or 
superheated waters, and we hold that the rock pressure, together with the influence 
of this moisture, would have been sufficient to cement the loose mass in very short 


Sixteenth Arm. Rept. U. S. Geol. Survey, pt. 2, 1895, pp. 70, 161. 








196 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


time, so that fissures could have been formed in it. But we believe that the wide¬ 
spread rock alteration in the breccia is so closely similar to that observed in veins 
that it was in all probability caused by the same or very similar waters, which we 
believe did not gain general access to the upper part of the volcano until breaks 
caused by the settling volcanic mass afforded them an ascending path. 

Among the evidence offered by Penrose to substantiate the theory of an early 
period of metasomatism is the fact that the pyrite of the altered breccia rarely con¬ 
tains gold. The same thing applies, however, practically to all of the pyrite in the 
district, which, whether in veins or in rock, seems to contain an important amount 
of gold only when admixed with tellurides. The altered breccia is, moreover, quite 
commonly cut by little seams which may be rich in crustified tellurides. In the 
massive rocks, especially syenite and latite-phonolite, where the solutions circu¬ 
lated less easily, the localizing of general pyritization near the veins is much better 
marked than in the breccia. 

EVIDENCE OF AQUEOUS ACTION. 

In their general aspect the metasomatic changes in the rocks by the vein-forming 
agencies clearly indicate aqueous solutions. As long ago pointed out by Bunsen in 
his researches on the fumaroles of Iceland, and as recognized by Penrose, 0 the 
strongest evidence of this consists in the removal of certain constituents, such as 
lime and soda, which neither are volatile alone nor enter readily into combination 
with any gaseous solvents. Further evidence is afforded by the deposition in regular 
layers shown in the seams cutting the altered rock. The widespread occurrence 
of earthy carbonates as a product of alteration also points in the same direction as 
does the general mode of attack on the rock by the solvents. We believe it to be 
firmly established that the metasomatism has been effected by aqueous solutions. 
That gases, such as carbon dioxide and hydrogen sulphide, were present in abun¬ 
dance is indicated by the general distribution of calcite, dolomite, and pyrite through 
the rocks, but these gases were present dissolved in water. The H 2 S might possibly 
have been replaced or aided by Na 2 S, though the extremely wide distribution of 
pyrite rather points to an easily diffusible gas. Both Cross and Penrose 6 express 
their belief that some volatile compound of fluorine may have been present, 
especially to effect the deposition of fluorite and the formation of the peculiar 
replacements known as granite ore. We can not share this belief, holding that both 
cases can easily be accounted for by deposition from alkaline solutions. 

OXIDATION. 

With few exceptions, and these on Beacon Hill and Poverty Gulch, the telluride 
ores near the surface are always oxidized to a brownish, claj^ey material. This 
oxidation along the veins naturally extends to far greater depth than the general 
oxidation of the country rock, and a partial oxidation may be found even at depths 
of 1,200 feet: It is very common to find brown streaks, due to limonite, following 
the narrow seams of the lode, while the surrounding breccia or massive rock 
appears entirely free from oxidation. 


" Sixteenth Ann. Rept. U. S. Geol. Survey, pt. 2, 1895, p. 100. 


<> Op cit., pp. 69,161. 




PROCESSES OF ALTERATION-OXIDATION. 


197 


ORIGINAL WATER LEVEL. 

According to the few data available, the original water surface of the district 
stood at an elevation of about 9,500 feet in the western part. Doubtless it rose 
slightly underneath the Bull Cliff region, reached 9,557 (910 feet below the surface) 
in the Isabella mine, and is even reported at 9,730 (516 feet below the surface) in 
the Hull City mine. In the southeastern part of the district the original water 
level in the Portland stood at 9,459, or about 540 feet below the collar of Xo. 1 shaft; 
in Stratton’s Independence at 9,576, or 274 feet below the surface; and in the Gold 
Coin mine at 9,403, or 368 feet below the surface. 

ROCK OXIDATION. 

As stated above, the general oxidation of the rocks does not correspond to the 
water level, but ceases long before the latter has been reached and usually at a 
depth of at most 200 feet below the surface; sometimes, and especially in the case 
of massive rocks, such as granite or latite-phonolite, fresh material appears a very 
short distance below the surface. At Stratton's Independence the oxidation of 
the breccia is only partial at a depth of 100 feet below the surface. To the general 
rule given above there are one or two notable exceptions. Over a large area on 
Globe Hill, embracing the Deerhorn, Lady Stith, Plymouth Rock, and Ironclad 
shafts the breccia is throughly oxidized and traversed by irregular systems of joints 
and short fissures. Globe Hill is opened in depth by the Chicago tunnel, the portal 
of which is located near the Abe Lincoln mine and has an elevation of about 9,700 
feet; the total length is 4,200 feet and it extends to the vicinity of the Plymouth 
Rock shaft. For the greater distance from the portal the tunnel is in unoxidized 
breccia, but 1.200 feet from the breast evidences of oxidation begin to be apparent, 
and near the end, about 700 feet underneath Globe Hill, the breccia is entirely 
disintegrated, forming a soft, clayey, red material which necessitates stout timbering. 
This condition extends at least to the bottom of the Plymouth Rock shaft, about 
150 feet below the tunnel level, or an elevation of 9.550 feet. Similar complete 
oxidation reaches at least to 700 feet below the surface in the Ironclad shaft. In the 
middle of this area is located the Deerhorn shaft, the lowest level of which is 565 
feet below the surface. Exploratory crosscuts extend from this shaft 600 or 700 feet 
in several directions without change of formation. A mass of gypsum, with some 
fluorite and a little pyrite, is exposed in the lower 300 feet of the shaft (p. 284). 
Oxidized material appears to surround it on all sides. The explanation of this 
unusually deep oxidation is probably that extensive shattering preceded a local 
and very intense thermal-spring action, which by dissolving much material rendered 
the breccia so porous as to fall an easy prey to oxidizing processes. A somewhat 
similar case is that of the Wild Horse mine, where the shattered and pyritic granite 
breccia, as well as the vein contained in it, is entirely oxidized to a depth of 1,150 
feet, or to an elevation of 9,500 feet. 



198 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


VEIN OXIDATION. 

In a very general way the depth of oxidation of the veins coincides with the 
depth of the water level, but here again there are numerous exceptions and quali¬ 
fications to be noted. Fresh tellurides often occur high above the water level, 
especially in hard and massive rocks. On the other hand, partial oxidation is in 
many cases apt to extend for several hundred feet below that level. 

At the Abe Lincoln and Beacon Hill mines unaltered tellurides appeared 
practically at the surface, as woidd be expected from the high stand of the water 
level at these mines, the elevations of which are 9,611 and 9,370 feet. But the 
same applied to the Gold King and C. O. D. mines, high up in Poverty Gulch, with 
elevations of about 9,850 feet. At the Moon-Anchor mine, on Gold Hill, oxidized 
ore extended down to the 600-foot level, or to an elevation of 9,200 feet. At the 
Doctor-Jackpot mine oxidation reached only a short distance below the surface 
in the Jackpot vein, while in the Doctor vein the ores were oxidized down to a depth 
of 650 feet below the surface, or an elevation of 9,078 feet. 

On Bull Hill the water level should lie about 700 feet below the surface, or at 
an elevation of 9,600 feet, although no accurate observations are available because 
the region was drained by tunnels long before the shaft had attained its depth. 
At many of the small mines on this hill tellurides were, however, met much higher 
than 700 feet. The Zenobia vein is entirely oxidized down to a depth of 500 feet. 

In the Last Dollar the veins are entirely oxidized above the 800-foot level, or 
above an elevation of 9,600 feet. Below this unaltered tellurides form the ore. 
The adjoining Modoc mine contains in places oxidized ore down to a depth of 
1,000 feet, although some tellurides were found on level 2. The Gold Sovereign 
mine shows partial oxidation to at least 550 feet, and on that level one-half of the 
Lovett vein is almost fresh, while the other half is entirely oxidized. 

The water level of the Isabella mine was probably 900 feet deep (elevation 
9,557) and complete oxidation of the veins certainly reached that depth in the 
breccia, partial oxidation being noted at least 100 feet lower. But in the latite- 
phonolite of the Buena Vista incline, on the same vein, tellurides were found on 
level 2 and on the lower levels the vein is scarcely attacked by oxidation. 

On the south slope of Bull Cliff both water level and vein oxidation are deep. 
At the Hull City mine partial oxidation reaches down to 850 feet below the sur¬ 
face, while the original water level is reported as being only 516 feet deep. At the 
Vindicator mine the first water was found at 500 feet, or at an elevation of 9,700 feet. 
All veins are oxidized down to this level, and to some extent even down to the 
800-foot level. The country rock is chiefly massive latite-phonolite. In the Golden 
Cycle mine, where breccia predominates as country rock, energetic oxidation has 
penetrated to unusual depths. The natural water level is unknown, but was, at 
any rate, less than 800 feet below the collar. The surface elevation is 10,066 feet, 
and the original water level may be tentatively given as at 9,500 feet, or 566 feet 
below the surface. Vein oxidation goes, however, much deeper than this, for 
between the 800- and 900-foot levels the veins are almost completely oxidized; a 
small amount of tellurides is, however, found in many places. The deepest level, 
1,000 feet below the surface, was under water at the time of visit. 


PROCESSES OF ALTERATION-OXIDATION. 


199 


The only generalization which can be safely deduced from all these data is 
that the limit of complete vein oxidation as a rule coincides with the water level, 
but that in many cases this process may partially, rarely completely, alter the 
veins for about 300 feet below this water surface. Owing to the peculiar conditions 
of underground drainage in Cripple Creek, it is unlikely that the water level has been 
subjected to great fluctuations. It may have been somewhat higher, but it is 
doubtful whether it ever stood much lower than when the district was first dis¬ 
covered, for, as stated in the chapter on the ground water, the volcanic mass holds 
water somewhat like a sponge in a cup. At any rate, no evidence indicating notable 
fluctuations can be adduced. 

STRUCTURE OF THE OXIDIZED VEINS. 

Thorough oxidizing decomposition will destroy the original structure of this 
vein. In sheeted lodes with many small parallel fissures and joints the latter may 
become effaced and the lode appears as a homogeneous brown, soft mass. In other 
cases a central seam may be retained and usually appears as a streak of soft, more 
or less impure kaolin; in other cases it maybe filled by white compact alunite, more 
rarely by jasperoid or opaline silica. Crusts of comb quartz, if originally present, 
lie included in the clayey seams, but neither the original fluorite nor the carbonates 
are ordinarily preserved. Ver} T rich oxidized ore sometimes fills the central cavities 
of the lode like a thick brown mud of limonite, kaolin, and quartz sand, and easily 
flows out when the vein is opened. Such material often fills the open seams in veins 
where the oxidation is only very partial, as in level 12 of the Gold Coin mine. When 
this level was unwatered, after having been allowed to fill up and stand for a long 
time, the floor was found to be covered by a thick mud up to 2 feet deep, which was 
said to have contained 2 ounces of gold per ton. The Dorothy vein here consists 
of one main seam in granite, coated with quartz, fluorite, and tellurides, besides 
some pyrite, zinc blende, and galena, and normally showing an open space in the 
center a couple of inches wide. 

OXIDIZING PROCESSES. 

In general oxidation tends to transform sulphides, sulphosalts, and tellurides 
to oxygen salts and native metals, both of which may, under certain circumstances, 
be further changed or carried away by surface waters. The silicates in the veins 
are changed to a few minerals most stable under atmospheric influences, i. e., 
kaolin, quartz, manganese dioxide, and limonite. Th6 carbonates of the earthy 
metals are carried away in solution, while those of manganese and iron are changed 
to oxides. As waters of acid reaction, frequently containing free sulphuric acid, 
prevail during oxidation of vein deposits, original quartz will not be attacked. 
New silica, generally hydrated, may be deposited by solutions derived from the 
decomposition of the silicates. 

The processes are more difficult to follow and to establish by means of analyses 
than those due to primary vein formation, for it seems to be a characteristic feature 
of oxidation to segregate the new minerals in larger masses and thus produce a 
less homogeneous product; this is no doubt due to the energetic action of oxygen 


200 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


and of the acids set free, as well as to the increasing mobility of substance near the 
surface. Oxidation tends to thorough change of composition and also to oblitera¬ 
tion of structure of the original rock or vein. 

Of the metallic minerals the tellurides form the most important division. 
The bond between the tellurium and the gold is not a strong one, and direct 
oxidation very easily produces residual pseudomorphs of free gold and tellurium 
dioxide (the mineral tellurite), which in presence of iron oxides easily changes to 
various tellurites such as the yellowish-green emmonsite. In the Bonanza King 
lode of the Midget mine occur veinlets of pyrite with tellurides. Within 30 or 40 feet 
of the surface oxidation has changed the tellurides to specks of native gold, while 
pyrite remains practically unaltered. The tellurides in fissures and joints, which 
form the most common mode of occurrence, will be most easily oxidized, while 
those occurring as metasomatic products in the rocks are not so readily reached 
by the surface waters. An instance of this occurred on the rich pocket of the 
generally oxidized W. P. IT. vein, 250 feet below the suface. Some of the tellurides 
are found here as replacement in schist fragments and remain partially fresh at 
this relatively shallow level. 

Pyrite also is attacked without much difficulty, especially in the vein fissures, 
and yields sulphuric acid and ferrous sulphate, which is easily oxidized to ferric 
sulphates and finally into ferric hydrate and free acid. The sulphuric acid attacks 
kaolin and probably also sericite, forming segregations of such impure alunite as 
is encountered, for instance, in the Last Dollar veins (p. 377). 

Small quantities of basic ferric sulphates are fairly common in the oxidized 
zone, but can rarely be referred to definite mineral species (p. 125). 

The rapid oxidation of pyrite is well illustrated by bowlders of breccia, con¬ 
taining 2 per cent of finely distributed pyrite, such as were found in surface pits 
near the C. O. D. mine. The rock consists of a normal breccia of granite, and 
phonolite, with much fine material. Angular fragments of phonolite are up to 
2 cm. long. A dark-brown skin covers the surface of the bowlders and evidently 
consists of limonite. Underneath it lies a light-gray zone of breccia, up to 1 cm. 
thick, while the center consists of the normal dark-gray breccia. Examination 
under the microscope shows that the only difference between these zones is that 
in the outer light-gray layer the pyrite has completely disappeared without leaving 
any limonite. No other changes are apparent in the rock. The pyrite has evi¬ 
dently been oxidized to sulphates and these have been carried to the surface by 
capillary action, there to be changed to limonite. 

Galena and zinc blende are probably somewhat less easily attacked than 
pyrite, but eventually become oxidized, and when changed to insoluble lead sulphate 
and zinc silicate may remain or even be somewhat concentrated into the altered mass. 

The molybdenite oxidizes very readily to yellow and blue molybdite and 
ilsemannite, and these products do not seem to be easily carried away. Tetrahedrite 
yields various forms of oxidized copper compounds, which, as usual, show considerable 
mobility. No oxidized products containing antimony have been recognized. The 
fluorite upon exposure to oxidation loses its deep-purple color and becomes dis¬ 
integrated. Eventually a part of it is dissolved in surface waters. 


PROCESSES OF ALTERATION-OXIDATION. 


201 


The altered rocks in the veins contain orthoclase, sericite, chlorite, dolomitic 
carbonates, and magnetite, together with a small portion of biotite, augite, and 
hornblende which have resisted the alteration due to vein-forming action. The 
most prominent product of oxidation is kaolin, which often becomes segregated 
in large, pure-white masses. The iron-bearing minerals are converted to limonite, 
and the manganese in the silicates, and especially in the carbonates, separates as 
earthy pyrolusite or as wad. During these processes some silica becomes con¬ 
verted to the soluble state, and there is reason to believe that the oxidizing waters 
in places are rich in this constituent. This was particularly observed in the Zenobia 
mine down to the 500-foot level, where a slimy opaline'silica seems to be deposited 
at the present time. Another evidence is in the occurrence of residual pseudo- 
morphs of gold after tellurides, the spongy gold showing a coating of opal. In 
places the silica will be deposited as chalcedony or jasperoid colored red in various 
tints by ferric oxide. 

The reaction between free sulphuric acid and the earthy carbonates produces 
gypsum, which has been noted at many points in the oxidized ores. The large 
mass of this mineral in the Deerhorn mine is, however, probably not formed during 
oxidation, but is more likely a primary deposit by hot waters. By the same reaction 
epsomite (hydrous sulphate of magnesia) and mallardite (hydrous sulphate of 
manganese) will be formed, and, being very soluble, frequently form a coating or 
effervescence on the walls of the mine workings in the upper levels. Zinc sulphate 
occasionally enters into these complex salts. Hydrous sodium sulphate and 
aluminum sulphate appear in the same manner and are evidently formed by com¬ 
bination of sulphuric acid with the soda set free during processes of kaolinization. 
A little potassium is contained in these sulphates, but the greater mass of this 
substance is tenaciously held in the rocks. The vein-forming processes involve a 
development of potash micas and potash feldspars from silicates containing sodium, 
and also from the orthoclase. The same tendency seems to persist in the oxidized 
ore to some extent, though well-defined micas are not known to develop. It is a 
well-known fact that some phonolites upon weathering are apt to become richer 
in potassium and poorer in sodium . a At any rate, the sericite due to vein-forming 
action tenaciously resists oxidation. 

A black or dark-green hydrous ferric sulphate is sometimes encountered as a 
soft filling of cracks and fissures of the oxidized zone. When dry it assumes a yellowish 
brown color, and is in all probability identical with chloropal or with the mineral 
morencite^ recently discovered in the Clifton copper mines of Arizona., 

Phosphates are sometimes found in considerable quantities in oxidized ores, 
indicating local concentrations during the process. 

In 1894 Dr. Richard Pearce, of Denver, contributed some important notes 
to the subject of oxidation of Cripple Creek ores. c He examined a specimen of 
ore from the Moose mine, evidently a partially replaced volcanic rock, one half 
of which was oxidized while the other half had remained fresh. 


a Roth, Allgemeine Geologie, vol. 2, p. 255. 

!> Am. Jour. Sci., 4th ser., vol. 18, December, 1904, p. 455. 
c Proc. Colorado Sci. Soc., vol. 5, 1894-1896, pp. 11-16. 



202 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


Partial analyses of oxidized and fresh ore from the Moose mine. 


[Analyst, F. C. Knight.] 



Unoxi¬ 

dized 

portion. 

Oxidized 

portion. 


Unoxi¬ 

dized 

portion. 

Oxidized 

portion. 

Silica. 

56.70 

50.55 

Sulphur. 



Alumina. 

19.35 

19.93 

Sulphur trioxide. 


2.55 

Iron. 

4. 20 


Tellurium. 

. 10 


Ferric oxide. 


10.57 

Tellurium oxide (TeO). 


.79 

Magnesia. 

.37 

.12 

Silver. 

.022 

None. 

Alkalies (by difference). 

.13.967 

12.131 

Gold. 

.041 

.049 


. 27 




Water. 

.50 

3.05 


100 

100 


In the fresh portion only 1.35 per cent of the alumina was soluble in hydro¬ 
chloric acid, while in the oxidized portion 3.18 per cent proved soluble. In the 
latter a hydrated basic ferric sulphate was proved to be present. 

In order to obtain further light upon the results of oxidation, some very rich, 
wholly oxidized ore from a vein in the breccia on the 100-foot level of Stratton’s 
Independence mine was obtained through the kindness of Messrs. C. M. Becker 
and W. N. Travell, of the mine staff. The soft, dark-brown, powdery ore in two 
samples from different places was subjected to analysis by W. F. Hillebrand with 
the following result: 

Analyses of oxidized ores from Cripple Creek. 



1. 

2. 


1 . 

2. 



54.45 

BBO. 

0.0025 

0.0025 

Ti0 2 . 


.80 

M0O3. 

.018 

.008 



14. 45 


.36 

. 19 



a 9.94 

Au. 

.35 

.52 

MnC >2 . 


1. 71 

Ag. 

None or trace. 

.02 

CaO. 


1.14 

so 3 . 


. 10 

MgO. 


.48 

p 2 o, . 

. 

.50 

K 2 0. 


9.96 

h 2 o. 



Na20. 


. 41 * 

co 2 . 


Trace. 

ZnO 


c 53 




CuO.'. 

0.03 

.03 



95. 4205 

PbO. 

. 

.18 





a Both Fe20 3 and FeO present. & Both MAO 2 and MnO present. c Possibly high. 

There are no sulphides. The difference is largely made up of combined water. 


From the analyses and from what is known about the normal composition of 
unoxidized ore the following conclusions may be drawn, although it is of course 
realized that much more analytical work would be necessary for an exhaustive 
treatment of this difficult subject. 

During oxidation the percentage of silica decreases moderately, probably by 
solution of silica set free during the decomposition of silicates. Alumina remains 
fairly constant, though it may locally concentrate to pure kaolin. The iron is apt 
to locally increase by concentration as limonite, though a part will be carried away 
as sulphate. Small amounts of lime and magnesia are probably leached from the 











































































PROCESSES OF ALTERATION-OXIDATION. 


203 


rock, but the quantity is not greatly changed. Manganese is greatly concentrated, 
locally, on the seams of the rock. As to alkalies, the accumulation of potassium 
begun during the vein-forming process is continued or at least maintained during 
oxidation. Pyrite is converted into sulphuric acid and sulphates, and the per¬ 
centage of sulphur is greatly decreased in the oxidized ore. Part of it remains as 
sulphate, but as there appears to have been no corresponding decrease of the bases 
it would seem likely that a considerable part of it was carried away as free acid. 
Little change is noted in the titanium, while phosphoric acid and zinc appear to 
have increased. The small quantities of other metals do not seem to differ notably 
from those observed in fresh vein material (p. 172). An increase of water to 3 or 5 
per cent is a natural consequence of the formation of kaolin and other hydrated 
salts; locally it may increase up to 14 per cent, which is the amount contained in 
pure kaolin. 

INFLUENCE OF OXIDATION ON GOLD, SILVER, AND TELLURIUM. 

In gold-quartz veins of the ordinary t} r pe it is common to find a very decided 
enrichment in the oxidized part of the deposit, due chiefly to a considerable reduc¬ 
tion of volume of the ore by solution and removal of many of the constituents, 
mainly of the sulphides. In some cases a solution and reprecipitation of gold may 
have taken place, but this is assuredly not the rule. It is also common to find that 
a very decided leaching of silver has taken place in the upper part of oxidized veins 
containing this metal, and this leaching is often accompanied by deposition of 
chloride or native silver at moderate depth, and by argentite and other secondary 
silver-bearing minerals in a zone a short distance underneath the water level. 

There is little indication of any decided enrichment of the oxidized ores in the 
Cripple Creek district. Owing to the structure of the veins and the small quantity 
of sulphides present, the reduction of volume of the oxidized veins is very slight; 
in fact, under certain circumstances an increase of volume may take place. The 
fresh telluride ore is apt to be extremely rich in places and high-grade pockets occur 
impartially in oxidized and fresh portions of the veins. The richest ore ever shipped 
from the district came from a depth of about 500 feet in the El Paso mine, where 
almost no oxidation occurs, even at the surface. 

Whether a slight enrichment has taken place or not is not easy to decide. We 
incline to the belief that the oxidized ores as a whole are somewhat richer than the 
corresponding telluride ore. The results obtained by Pearce on the specimen from 
the Moose mine mentioned above (p. 201), one-half of which was oxidized, tend in 
the same direction. The fresh portion contained 12.24 ounces gold per ton, while 
the oxidized portion yielded 14.58 ounces. This difference may, however, simply 
depend upon unequal distribution of the gold. 

Regarding the silver there is more decided evidence of leaching. Much silver 
occurred in the oxidized portions of the Moose and the Blue Bird veins* but there 
are no data from the production of the mines to show whether any leacliing has taken 
place. Pearce’s results would seem to indicate that a removal of silver had taken 
place during oxidation, for in the fresh ore he found 6.7 ounces silver per ton, while 
none was contained in the oxidized portion. The analyses of the oxidized ores of 
Stratton’s Independence tend also to show a removal of silver, as does the fact that 


204 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

the free gold of the ordinary oxidized ore is very often entirely free from silver. 
Possibly, as suggested by Pearce, the silver has been dissolved by ferric sulphate. 

No evidence has been found to show that any part of the gold set free by 
oxidation has been dissolved and reprecipitated. The silver dissolved from the 
oxidized ores should be deposited as chloride and native metal just above or as 
sulphides below the water level. No evidence has been found that this process 
has taken place. The quantity of silver in the veins is, however, usually very 
small. 

The analysis quoted in the paper by Pearce contains in the oxidized portion 
far more tellurium in oxidized form than would be required to form tellurides with 
the gold and silver. If this were a general fact it would indicate that a part of the 
gold had been dissolved. The two analyses by Hillebrand of samples from Stratton’s 
Independence mine (p. 202) show, on the contrary, a very considerable deficiency 
of tellurium, and it is in fact easily to be comprehended that the relatively soluble 
oxidized tellurium compounds could have been carried away or locally concentrated. 

SECONDARY SULPHIDE ENRICHMENT. 

If oxidation of a deposit is accompanied by leaching of one or more metals, like 
copper, silver, or lead, b} r surface waters, it sometimes happens that the materials 
dissolved from the oxidized part of the veins will be precipitated as sulphides at a 
lower elevation, and generally just below the water level. 

In districts where this so-called sulphide enrichment is known to have taken 
place the ore minerals exhibit in general an orderly sequence, both in relative 
abundance and in kind, from those characteristic of the most highly enriched ore 
to those constituting the original lean and unaltered ore. The secondary minerals 
produced are such as can result from rearrangement and concentration of elements 
present in different combinations in the primary ores. At certain points within 
this range of alteration it is possible to detect direct mineralogical evidence of the 
change of one mineral to another, effected by solutions moving downward from 
the zone of oxidation. In most cases the secondarily enriched ores bear a recog¬ 
nizable relation to the lower limit of oxidation. 

Careful study of the Cripple Creek ore deposits has failed to discover that the 
hypothesis of secondary enrichment is supported by crucial evidence of the kind 
just indicated. The minerals are not arranged in any discoverable sequence, nor 
does the present investigation find anything to support the view that the rich 
telluride ores, as a rule, pass with increasing depth into low-grade pyritic ores. 
Frequently such ore as occurs below a depth of 1,000 feet is precisely the same 
in character as ore found within 100 feet of the surface. Tetrahedrite, which has 
been regarded by some, without definite proof, as a secondary mineral, occurs 
sporadically throughout the district and at all depths reached by present workings. 
No particularly rich ore occurs immediately below the oxidized zone. Briefly, 
no evidence has been found indicating that sulphides or tellurides have been formed 
in or below the oxidized zone by deposition of material dissolved by surface waters. 


CHAPTER X.-THE ORE SHOOTS. 


It is well known that the payable ores in auriferous lodes are rarely equally 
distributed in the lode, but form tabular bodies of more or less regular outline. 
The projections of these ore bodies on the plane of the lode often appear as elongated 
areas with greater vertical than horizontal extent. The ore bodies or shoots of 
Cripple Creek show great similarity to those of other gold-bearing veins; their 
limit in depth is usually as well defined as their extent in a horizontal direction. 

The opportunities for the study of ore shoots have been exceptionally good in 
this district, as will be seen from a perusal of the detailed descriptions. If with all 
these observations there remain many doubtful and unexplaihed points in their 
occurrence, this must be laid to the great inherent difficulty of the subject. The 
deposition of ores depends not only on structural features, but also on imperfectly 
known laws of precipitation from complex solutions at high temperatures and 
pressures. 

DIMENSIONS AND PITCH OF THE SHOOTS. 

The general statement that the ore shoots are tabular bodies is based on the 
fact that the ore follows vein fissures and sheeted zones, and that consequently the 
thickness may be considered constant. In reality the thickness varies considerably. 
In some veins almost the whole value is concentrated in a central seam, although 
a width of 3 feet must be extracted on account of mining requirements. The most 
common case is that while the greater values are in one or two central seams a num¬ 
ber of others also contain friable ore, which is extracted by screening the whole 
thickness taken out, say 4 feet. Frequently, however, the width containing valuable 
seams increases to 10 or even 20 feet, while in exceptional cases of many coalescing 
sheeted zones the stopes may attain a width of 50 feet, as in the Captain veins of 
the Portland mine. In gold-bearing veins consisting of thick quartz filling it is not 
uncommon for a certain width of this vein to contain the valuable ore, while the 
remainder may be of very low grade. * Such a condition, which is apt to be caused 
by a reopening of the vein fissure and attendant enrichment, does not often occur 
in this district. A somewhat similar state of affairs has been observed in the Blue 
Bird mine, where the ore in places follows spar veinlets which are later than the 
main filling of “purple quartz.” 

If we assume that the shoot has an elongated, narrow shape, as usually is the 
case when projected on the plane of the vein, its geometrical relations may be des¬ 
ignated as follows; Width or thickness, breadth, stope length, pitch length, and 
pitch. The thickness or width has already been discussed; the stope length is the 
distance along the drifts over which payable ore extends; the pitch length, or 
axial length, as it might also be termed, is the distance between the two extreme 
ends of the shoot; the pitch is the angle which the pitch length makes with the 
horizontal; the breadth is the horizontal width multiplied by the sine of the pitch. 


13001— No. 54—66 


15 


205 




206 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

The slope length is subject to great variations. In small shoots it may be but 
a few feet, while in the majority of ordinary ore bodies characteristic of the camp 
this dimension ranges from 50 to 300 feet. In exceptional cases, as in the Elkton 
and Mary McKinney veins, the stope length is 1,700 or 2,000 feet. Owing to the 
prevailing steep pitch there is little difference between the breadth and stope 
length. The pitch in the great majority of cases is steep, ranging from 45° to 90°, 
and is generally northward, but there are also a number of southward-pitching 
shoots. In some mines adjoining veins have shoots of opposite pitch. Thus in the 
Midget mine the Cobb ore shoot pitches 45° NE., while in the Bonanza King vein 

the pitch is 60° SW. A south- 

CNOSS SECTION LONGITUDINAL SECTION J ., , . , , . . „ . 

ward-pitching shoot is also found 
in the Hoosier, Ironclad, Pinnacle, 
and Joe Dandy mines. Reversal 
of pitch is sometimes observed. 
In the C. O. D. mine the shoot, 
with an average horizontal length 
of 100 feet, pitches 40° S., but 
below level 6 turns and becomes 
inclined northward, at the same 
time decreasing in value. A simi¬ 
lar case was observed in the Gran¬ 
ite mine, where the principal shoot, 
with a greatest stope length of 350 
feet, pitches north from level 5 to 
level 7, while below it turns south- 

FI °- “-Diagram illustrating use of terms in descriptions of ore wftrd The greategt thickness i s 

30 or 40 feet. In case there are sev¬ 
eral shoots in one lode, these do not necessarily have the same form nor the same pitch. 

The pitch length of the shoot varies greatly. An average in the more impor¬ 
tant mines would probably be 500 feet, but this is very considerably exceeded in 
many cases. The Lillie-Yindicator and the Stratton’s Independence-Port land 
shoot (of the Independence No. 2 vein) are the longest actually proved, having 
attained 1,500 feet. The Cheyenne shoot of the Isabella mine is 1,250 feet long, 
and the same figures are recorded in the Wild Horse shoot. In other mines, like 
the Mary McKi nn ey and the Elkton, the true length is as yet undetermined. It 
is necessary to distinguish between absolute and truncated pitch length, the latter 
term applying to those shoots which have been truncated by erosion. The Chey¬ 
enne shoot of the Isabella mine is one of the few larger ones in which the absolute 
length has been measured. 

GENERAL FORM OF THE SHOOTS. 

The preceding discussion has assumed that the ore shoots have the normal 
elongated form which is ordinarily characteristic of them. There are, however, many 
exceptions, as will be seen from PI. XIX, which represents the outlines of a 
great number of Cripple Creek ore shoots. Ordinarily the ratio of pitch length 
and breadth for the ore shoots varies from 2 : 1 to 3 : 1. In the ore shoots which 
























U. S. GEOLOGICAL SURVEY 


PROFESSIONAL PAPER NO. 54 PL. XIX 


10500 


10500 


10500 


IOOOO 


9500 


9000 


10500 


jOOOO 


9500 


9000 


10500 


10000 


9500 




10500 


IOOOO 


9000 feet above sea level 


9500 


9000 



10500 


IOOOO 


9500 


9000 



10500 


IOOOO 


9500 


9000 


EXPLANATION 

Surface 



10 A/>Ore shoot 

W///////M 

Possible continuation of 
shoot below present 
developments 


SHAPE AND VERTICAL RANGE OF SOME OF THE PRINCIPAL 


ORE SHOOTS OF THE CRIPPLE CREEK DISTRICT, SHOWN IN LONGITUDINAL PROJECTION. 


















































































































































































































































































RELATION OF ORE SHOOTS TO SURFACE-. 


207 


begin distinctly below the surface the elongated form is more strongly accentuated, 
the ratio between pitch length and breadth varying from 1^:1 to 5:1. 

A few of the large ore shoots are practically equidimensional. This is more 
generall} 7- the case with the small shoots and here the horizontal extent is in a few 
instances greater than the vertical. 

Sometimes the outlines are wholly irregular, and as the exact limit between 
what are considered the payable and barren portions of the vein is an arbitrary 
one, depending on local facilities and price of production, areas are often left 
unstoped in the middle of a shoot which properly belong to it. The Gold Coin 
mine, for example, has stoped squarely up to the line separating this mine from the 
Dead Pine mine. The smaller Dead Pine mine, however, can not work this ore, 
which here happens to to be low grade, so that stope maps give the false impression 
that the Gold Coin ore body ends at the Dead Pine line. Where the shoot has its 
normal elongated form it is very common to find little pockets or irregular masses 
of ore just above and below the points where it begins or ends. Thus, in the Isabella 
mine, small masses of ore were frequently found in the lower levels underneath the 
places where the ore shoot is developed in force above. The same is observed at 
many other mines and may in fact be considered as a general rule. 

The outlines of the shoots are not usually limited by fissures or seams. Pen¬ 
rose describes such a case from the C. O. D. mine, and similar cases may be noted 
here and there. In the Gold Coin mine, for instance, the Cashen fault is the dividing 
line between the barren and the productive zone. Ordinarily, however, there are 
no such limiting seams. On the contrary, the ore gradually grows thinner and 
poorer toward the outside, begins to get bunchy, and finally ceases altogether, 
while the vein may continue as before in its general character, except that the 
calaverite is absent. Frequently, however, the limit of the ore shoot is attended 
with diminution in the width and strength of the sheeted zone. 

When one ore shoot ceases in depth it is often observed that another one, 
somewhat overlapping, is apt to come in on an adjoining fissure. In some lodes 
the ore shoot as a whole is really a succession of imbricated bodies on adjoining 
planes. 

Thorough exploration of the surroundings of a prominent ore shoot will prob¬ 
ably be rewarded by the discovery of smaller bodies underneath, in the main 
direction of pitch. 

RELATION TO SURFACE. 

Of 60 pay shoots of Cripple Creek mines plotted together for purposes of com¬ 
parison, 30 extend from the surface to a depth of less than 500 feet. The maximum 
individual production of these is less than $1,000,000. 

Near 6 of these ore bodies further exploration developed new shoots below 
the old ones, but usually of smaller extent. In practically all 30 cases the devel¬ 
opment work had been carried down a few hundred feet below the last ore of the 
surface shoot. The form of these smaller shoots is often equidimensional; in a few 
cases the horizontal extent is greater than the vertical, or the shoot is wholly 
irregular; in many cases the shoot pitches steeply northward on the plane of the 
vein and the ratio of vertical to horizontal extent is 2:1 or 3:1. 


208 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


In 8 of the 60 cases the shoot extended from the surface to a depth of 1,000 
feet, or a little more, and ended. Further development to about 1,500 feet failed 
to find new shoots of any importance, though small pockets were often discovered. 
In 6 of these 8 cases the ratio of vertical to horizontal extent varies from 3:1 to 
5:1, and the shoots usually pitch northward at angles of 60° to nearly 90° from 
the horizontal. In the remaining 2 cases the shoots have about the same horizon¬ 
tal as vertical extent. The maximum horizontal length is 1,300 feet, while 400 is 
much more common. In 2 of the 60 cases the pay shoot is 1,500 to 2,000 feet 
long, maximum depths of 600 and 1,000 feet having been attained and the bottom 
level being still in ore. In 13 of the 60 cases the shoot began over 200 feet below 
the surface; in 8 of these the bottom of the shoot has been reached, while in 5 the 
lowest level is still in ore. Steeply dipping, irregular elongated forms prevail. 
Many of this group of 13 represent veins parallel and close to those on which pay 
shoots outcropping at the surface were found. 

These statements will give an idea of the form of the shoots. Of course, in 
the case of shoots reaching the surface, a certain part has .probably been removed 
by erosion. Judging from the shoots which distinctly began below the surface, 
the normal form of the ore bodies is elongated, vertical, or pitching sharply north¬ 
ward, the ratio of vertical to horizontal extension varying from 11:1 to 5:1. Some 
of these shoots are, however, of about equal dimensions, vertically and horizontally, 
while in a few the horizontal dimension is the greater. 

RELATION TO COUNTRY ROCK. 

In general the influence of country rock on the ore is ver}^ slight, and the causes 
governing the variations which may be detected are more apt to be due to physical 

differences relating to the 
Assuring in the various kinds 
of rock than to any chem¬ 
ical characteristics influenc¬ 
ing the ore deposition. Ore 
shoots occur in all of the 
various rocks cut by the 
vein, granitic as well as pho- 
nolitic. The best ore shoots 
are found in breccia, and 
this is probably due to its 
greater permeability and the 
greater width of Assuring in 
this rock. Very large ore 
shoots are, however, also 
inclosed by latite-phonolite 
and syenite, as well as by 
granite. As instances of the 
latter may be cited the gran¬ 
ite slopes in the Ajax, Portland, and Gold Coin mines, while the very important ore 
shoots of the Vindicator mine are almost exclusively contained in latite-phonolite. 



Fig. 15.—Cross section and longitudinal section of pay shoot in Prince Albert 
mine, showing its relation to phonolite sheet. 


















RELATION OF ORE SHOOTS TO COUNTRY ROCK. 


209 


Between the Findley and Hull City mines the ore shoot leaves breccia and enters 
into latite-phonolite without marked change in composition or value. On the 
other hand, latite-phonolite and syenite are notably unproductive in the Portland 
mine (PI. XXVIII, p. 434). 

The relations of ore shoots to bodies of phonolite are sometimes significant. 
In some places the ore shoots are enriched when entering phonolite, while in other 
cases they are distinctly and markedly impoverished. In the Elkton mine the flat 
ore body corresponds roughly to the outline of a body of phonolite in which it 
occurs between two lines of vertical fissures 120 feet apart. The ore in this case is 
confined to this flat body of phonolite. An interesting case showing the localiza¬ 
tion of an ore shoot by a phonolite sheet is shown in fig. 15 (p. 208), representing a 
pay shoot in the Prince 
Albert mine on Beacon 
Hill. In this case a verti¬ 
cal fissure system inter¬ 
sects a flat dike of phono¬ 
lite in granite. The ore 
has accumulated on the 
upper side of the dike, 
while below it there is only 
a very small quantity. It 
appears very much as if 
the solutions were locally 
descending and as if con¬ 
traction of the fissures in 

the more resistant phono- ^ig. 1(i -— Longitudinal section of the El Paso vein, showing form of ore body at 
.. i i 1 • [intersection with phonolite dike. 

hte prevented the active 

circulation and induced precipitation on its upper side. An instance somewhat 
similar to this, but on a much larger scale, occurred in the Isabella mine; the Chey¬ 
enne ore shoot is suddenly cut off just below level 10, where the fissure leaves 
breccia and enters into a hard, compact phonolite. The richest part of the whole 
shoot was found here, resting immediately on top of the thick sheet of phonolite. 
Similar relations are said to have obtained in the adjoining Victor mine. 

The ore body of the El Paso lode on Beacon Hill has the form of a flattened 
ellipsoid lying against the under side of a phonolite dike, its longest axis pitching 
northeast with the general line of intersection of lode and dike. In this case also 
the dike probably limits the ore shoot by reason of being less permeable to the 
solutions than the surrounding granite. 

RELATION TO INTERSECTIONS. 

The factor which most obviously influences the position and extent of ore 
shoots is the intersection of veins with one another or with “basic” or phonolite 
dikes. That such intersections are favorable to the development of ore shoots 
must be regarded as a well-established law in this district, as well as in many others. 
In some cases it is found that intersections of two veins have an adverse influence 



E/ Paso tunre/ 










210 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


W 


Damon shaft 



on the ore shoot, locally depressing the values or wholly eliminating them. This, 
however, is exceptional. 

Although the location of ore shoots is so striking^ dependent upon intersec¬ 
tions of veins that it might at first glance be considered as the only factor influencing 
the distribution of the ore, this as will be seen further on, is by no means true. 
The ore shoots occur very commonly on intersections of veins, but this is observed 
chiefly in the case of smaller shoots and in smaller mines in which fissures intersect 
in various directions. The largest ore shoots in the camp can not be explained by 

the simple intersection of two or more 
fissures. In the occurrence of these 
smaller ore shoots along intersections 
the so-called “flats,” or gently dipping 
joint planes, are of especial importance, 
as bodies of ore are very frequently 
found where they cross the vertical or 
steep fissures. In some cases the pay 
ore occurs exclusively in the “flats,” 
but very close to the intersection, while 
in other cases the ore is contained chiefly 
in the steep veins and is suddenly cut 
out by gently dipping seams. Some 
very large bodies of ore have been found 
on these flat seams, which in themselves 
are rather inconspicuous. In the fol¬ 
lowing paragraphs a few examples from 
among the more important mines of the 
district will be given in order to illus¬ 
trate this remarkable dependence of 
shoots on intersections. 

In the Abe Lincoln the pay shoots now worked occur southeast of the shaft at 
the intersection of two or more of the individual, indistinct, and not very persist¬ 
ent fissure zones in gneiss. 

In the Jerry Johnson little ore was found down to the 300-foot level. At this 
place an ore shoot about 80 feet long occurred along the vein, but was cut off 40 
feet above the level Iw a flat seam. A similar flat seam cut off the values in the 
W. P. 11. vein. In other parts of the mine, however, the flat veins carry some ore. 
At the Damon mine (fig. 17) the principal ore bodies were found on several flat 
veins near the place where these intersected or joined a steep-dipping fissure. 

In the Howard flat vein an ore body, in places 6 feet thick, occurred where 
this vein was intersected by a perpendicular fissure. In the same vicinity the 
Work lode contained ore where it intersected No. 2 Mary McKinney lode. On the 
Anaconda adit level the breccia contains many fissures of various strikes and dips. 
Where two or more intersect there is usually a small body of ore. 

Although the main ore body of the Mary McKinney mine has no apparent 
connection with crossing fissures, many instances of the rule here discussed may 
be found in the northern part of the mine at the intersection of lodes. The Le Clair 




Volcanic breccia Schist St opes and vein 

Sea I e oF -feet. 

0 ioo 200 300 

i-1_i___» 


Fig. 17.- 


-Diagram of veins and stopes in upper levels of 
Damon mine. 













RELATION OF ORE SHOOTS TO INTERSECTIONS. 


211 


mine contains ore at the intersection of the Peggy vein with the north-south fissure. 
An ore body at the intersection of a sheeted zone with a dike in the Elkton mine 
is shown in fig. 36 (p. 338). 

Bull Hill also presents many examples. In the War Eagle mine the ore 
occurs in flat veins, but only along the intersection of these with the steep-dipping 
War Eagle vein. The Ramona vein in the same mine shows, however, an anoma¬ 
lous behavior; a small pay shoot occurring on it is abruptly cut off by a water¬ 
course crossing the vein. A similar case is observed in the Sheriff mines, where 
small shoots are cut off by flat quartz seams. 



Fig. 18.—Stereogram of ore shoots on the Pinto dike and Pharmacist vein in the Pinto and Wrockloff mines. 


The New Haven and Mary Ann mines show many illustrations of this prin¬ 
ciple. In the latter the intersection of flats with the north-south steep-dipping 
vein produces ore. Smaller bodies of ore were also found at the triple intersection 
of fissure systems. In the Ida May ore occurred in the basic dike, particularly 
where fissures came in from the walls. 

The Gold Sovereign, Whisper, and Dante mines contain many small ore 
bodies, most of which are dependent upon intersections of the complicated system 
of fissures which are found in these properties. In the Trail mine close by the 
intersection of two veins is said to have made the best ore in the mine. In the 
Dexter a good body of ore occurred where the Fluorite and Manganese veins unite. 










































































212 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 



re body 


loofeet 

i---i 

Fig. 19.—Plan showing occur¬ 
rence of ore bodies at inter¬ 
section of sheeted zone and 
phonolite dike in Dead Pine 
mine. 


Intersection of a vein with a narrow perpendicular seam gave a couple of carloads 
of good ore. • 

The long Orpha May vein, traceable from near the American Eagle shaft for 
a mile southward into the Modoc property, offers perhaps the best example in the 

camp of the influence of cross fissures on long lodes. Penrose 
states that in the Orpha May mine, the most northerly on 
the lode, the shoots were narrow, but more likely to occur 
wherever cross fissures intersected the vein. In the Rubie a 
long, narrow shoot occurred where an east-west vein inter¬ 
sected the Orpha May. It is illustrated best of all in the 
Last Dollar mine, in which the most important shoot fol¬ 
lows the intersection of cross veins with the main vein. In 
this case some ore is also contained on the former, but rarely 
extends more than 40 feet from the main vein. Further 
interest is given to this occurrence by the difference in ore 
carried on the two kinds of veins, the cross veins being rich 
in pvrite, zinc blende, and tetrahedrite, while only normal 
calaverite ore occurs on the 
main vein. Very similar con¬ 
ditions are observed in the 
Modoc mine, though the dif¬ 
ference in ore is not so marked here. ' 

Between the Isabella lode system and that of 
the Vindicator lie a number of cross fissures, most 
of them having a northeasterly strike. In the 
mines located on these veins a number of interest¬ 
ing occurrences may be observed. In the Empire 
No. 2 vein one pay shoot is clearly the result of 
the intersection with the Buena Vista vein of the 
Isabella system. At the Pinto mine the intersec¬ 
tion of the Pinto dike with the Pharmacist vein 
produces an important and rich shoot (fig. 18). 

Another on the same vein lies at the intersection 
of the Pharmacist and the Zenobia. In the Dead- 
wood mine intersection of vein systems is clearly 
connected with the occurrence of the ore. 

As a rule no influence of cross fissures can be 
observed in the great pay shoots of the Vindicator 
system. In one case, however, at the north end of 
the Findley, a small but rich shoot occurred at the 
intersection with an east-west cross vein. Where the same vein crossed the adjoin¬ 
ing and parallel Sliurtlofl vein the pay contained on the cross vein became locally 
impoverished. 

In the Golden Cycle mine the shoots are not, as far as can be observed, depend¬ 
ent on crossings. Frequently, however, the richest ore occurs at splits in the 
principal veins. This is illustrated in both the Legal Tender and the Revenue 
svstems. 



Fig. 20.—Diagrammatic plan showing occur¬ 
rence of ore body in granite on le^el 5, Ajax 
mine. 












RELATION OF ORE SHOOTS TO INTERSECTIONS. 


213 


Few examples of this rule may be derived from the Portland and Independ¬ 
ence mines. In the latter, however, the flat ore body occurring between levels 
3 and 5 may be regarded as a special case of the local expansion of ore bodies at 
the intersection of perpendicular veins with horizontal flats. 

The description of the Granite mine shows that in all cases unusual width of 
ore is associated with intersections or junctions of main lode with minor fissures. 
In the adjoining Dillon mine ore occurs chiefly in bunches at 
the intersection of sheeted zones. An example from the Dead 
Pine mine is shown in fig. 19. 

The Ajax mine is characterized by the presence of large 
and irregular bodies of replacement ore in granite. The occur¬ 
rence of these shoots is clearly related to the intersections of 
the two northeast-southwest phonolite dikes with the numerous 
northwest-southeast fissures (figs. 20 and 21). 

The Sunset-Eclipse mine, on the west side of Squaw 
Mountain, offers an illustration on a small scale. A body cf 
ore occurs here at the intersection of three fissure s}^stems. 

All these examples, the number of which could I e 
greatly increased, show clearly that deposition of tellurides 
is strongly and most favorably influenced by intersections of 
fissures. A mingling of different waters may obviously have 
occurred at such intersections and it is almost self-evident 
that such conditions might easily either excite or check the 
precipitation of certain compounds dissolved in the waters.® 

The different mingling waters may well have come from one source, although 
by traveling separate ways for a distance their character may have been sufficiently 
changed to influence the precipitation of some compound. 



o 


Scale 


50 ft 


Fig. 21. —Plan of an ore body 
in granite, level 4, Ajax 
mine, showing influence of 
contact between granite 
and breccia and phonolite 
dike in determining the 
place of ore deposition. 


OTHER FACTORS. 


A close study will soon convince one that the ore shoots directly due to inter¬ 
section are usually the smaller ones, and that although this factor is almost obtru¬ 
sively present, it is by no means the only one nor the most important. Examples 
of ore shoots apparently entirely independent of intersections would include the 
largest shoots in the camp. Among them are the Mary McKinney, Elkton, Moose, 
Vindicator, Golden Cycle, Hull City, Findley, Isabella, Portland, Stratton’s Inde¬ 
pendence, and Victor. 

It might be suggested that here, too, intersections are the cause, hut that they 
have not been observed. This, however, is improbable, for either the miner, who 
is very much on the alert for just such features, or the geologist should easily have 
recognized them. The great size of the bodies and the even distribution of the 
ore forms another argument against such a supposition. 

Wddbelieve that in these cases other causes favoring precipitation become 
operative, such as decrease of pressure and temperature, and gradual change of 
solution by diffusion, absorption, and chemical action, rather than intermingling 

a Regarding the influence of intersections, see, for instance, Van Hise, C. R., A treatise on metamorphism: Mon. U. S. 
Geol. Survey, vol. 47, 1904, pp. 1082, 1223. 







214 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


of different waters. It is also to be remembered that a single local precipitation of 
tellurides will instantly act as an incentive to further precipitation and that the 
law of mass action is apt to produce cumulative effects. 

INFLUENCE OF DEPTH. 

Of the known ore bodies, as few exceed 1,000 feet in horizontal width, so very 
few exceed 1,000 feet in length or extend more than 1,000 feet from the surface. 
To speak broadly, explorations below that limit have not proved very satisfactory. 
With the lines drawn a little closer, it may be said that in proportion to the amount 
of exploration the upper 700 or 800 feet have yielded more than the interval from 
that limit to the lowest levels reached—-about 1,500 feet. It must not be over¬ 
looked, however, that four or five mines still have good ore bodies at a depth of 
1,200 to 1,400 feet from the surface. The developments of the next year or two 
will probably give a safer basis for generalization. 

In a general way, the above-mentioned distribution holds good for any eleva¬ 
tion within the district. In other words, the principal productive zone everywhere 
occupies the space from the surface down to about 1,000 feet below it, and its 
lower limit forms a curved surface approximately parallel to the surface of the 
ground. The fact that one mine situated in a low part of the district may have an 
ore body 2,000 feet below the shaft collar of another mine in a high part of the 
district is thus entirely in harmony with this statement. 

The question now arises, How far does the distribution of known pay shoots 
represent the distribution of all the pay shoots in the district? In other words, 
How far has exploration been impartial in revealing ore bodies near the surface 
and at depths greater than 1,000 feet? 

It requires but little examination to make clear the fact that ore bodies within 
1,000 feet of the surface are far more likely to be discovered than those at greater 
depth. While shafts have been sunk for a few hundred feet without any indica¬ 
tion of ore and have ultimately been developed into productive mines, such a pro¬ 
cedure is considered bold prospecting, and few well-informed mining men would 
seriously contemplate sinking a shaft over 1,000 feet solely on the expectation of 
finding possible ore bodies below that depth. Most of the large mines in the district 
have started upon some indication of ore near the surface and have grown by the 
subsequent discovery of other lodes and ore bodies in the course of their underground 
development. As few individual ore bodies persist for more than 1,000 feet in 
depth, by far the greater part of the underground prospecting is at less depths, 
there being usually little inducement to go deeper, unless, as in the case of the 
Gold Coin and Portland mines, lodes are discovered in which the ore, beginning 
several hundred feet below the surface, extends deeper than the pay shoot upon 
which the mine was originally opened. Thus deep prospecting is usually confined 
to the vicinity of the larger and more persistent pay shoots which have been fol¬ 
lowed down from near the surface. Underground water has also proved a most 
serious obstacle to deep prospecting, few properties being able to develop below the 
1,000-foot zone unless there is abundant and high-grade ore in sight. 


INFLUENCE OF DEPTH ON ORE SHOOTS. 


215 


It may thus be concluded, without necessarily advocating promiscuous explo¬ 
ration below the 1,000-foot zone, that any ore bodies existing below that depth are 
far less likely to be discovered than those above, where from the surface to depths 
of several hundred feet the rocks of the district are riddled with shafts, drifts, 
crosscuts, and adits. It is difficult, however, to determine the relative importance 
of this factor in the problem. It is probably safe to assume that the chances of 
discovering a given ore bod}' within the 1,000-foot zone are at least ten times those 
of discovering an ore body below that zone, and the ratio may be very much greater. 
While it is also very probably true that there was originally more ore within the 
1,000-foot zone than there is in a corresponding zone below, this disparity is not 
necessarily anything like so great as is indicated by the vertical distribution of 
known pay shoots. 

Another important line of inquiry bearing upon the relations of the ore bodies 
to depth is concerned with the question of the relative size and abundance of the 
fissures near the surface and at greater depth. It has been shown that all the ore 
bodies are intimately connected with fissures. If such fissures are generally smaller 
and less abundant below the 1,000-foot zone than they are within it, obviously 
there is introduced a factor which diminishes the supposed importance of secondary 
enrichment by affording an anterior and physical explanation for the decrease of ore 
with increase of depth. 

Detailed examination of practically all the accessible mines in the Cripple Creek 
district has led to the conclusion that the fissures, which ordinarily are narrow and 
often appear as mere cracks, do become less abundant and less conspicuous as 
greater depth is attained. No mine exhibits this feature better than Stratton’s 
Independence, in which the very complex systems of productive fissures on the 
fifth and higher levels contrast most strikingly with the few insignificant and 
unproductive fractures visible on level 14. In less degree the same feature is shown 
in many others of the deep mines, but the rule is not without some very marked 
exceptions. 

There are thus at least two factors to account for the smaller development of 
ore shoots below the 1,000-foot level: First, difficulties of development and explo¬ 
ration; and, second, the disappearance of many fissures in depth. These two do 
not, however, seem to completely explain the facts, and it is believed that there is 
a' third cause which is related to temperature and solubility and which favored 
deposition near the surface rather than in depth. 

The minimum depth of rock removed from the district by erosion may be esti¬ 
mated to be 1,000 feet in the central part and 400 or 500 feet about the periphery 
(p. 38). Possibly it was somewhat more. The shape and number of the ore bodies 
formerly existing in this eroded zone can be only conjectured, but it is probable 
that they were large and numerous. The veins were evidently formed shortly after 
the close of igneous activity, while the volcano yet possessed a greater height than 
at present and had a more or less pronounced conical shape. 

If further development substantiates the dependence of the maximum devel¬ 
opment of the ore shoots on the depth from the surface irrespective of the elevation 
of the croppings, this would, according to the preceding explanation, be due partly 


f 


21(5 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

to the more abundant Assuring within the surface zone of a conical volcanic moun- 
tain and partly to the parallelism of the underground isothermal surfaces with the 
surface slopes, for these surfaces would determine the depth at which the most 
active precipitation took place. 

It is believed that the vein-forming solutions ascended rapidly on a few domi¬ 
nant and very deep fissures and that they were distributed from these throughout 
the volcanic rocks, diminishing their velocity and gradually changing their compo¬ 
sition. This would help to explain the scarcity of ores in depth and the frequent 
precipitation by mingling waters at the intersection of fissures. Decrease of 
temperature and retardation of water currents are regarded as the main factors 
favoring precipitation of the tellurides. 




> 


I 


I 



CHAPTER XI—GENESIS OF THE DEPOSITS AND PRACTICAL 

CONCLUSIONS. 

ORIGIN OF THE ORES. 

COMPOSITION OF THE VEIN-FORMING WATERS. 

GENERAL STATEMENT. 

From the metasomatic action, from the fissure fillings, and from other data 
certain conclusions may be drawn, regarding the characters of the vein-forming 
solutions, although our imperfect knowledge of the chemical activity of thermal 
waters under the influence of high temperature and pressure is as yet an obstacle 
to the clear understanding of their work in depth. This is a field in which intelligent 
experimentation will yet accomplish substantial progress. 

The general alkaline character of the waters with strong percentages of hydro¬ 
gen sulphide, silica, alkaline carbonates, and sulphates may be considered as firmly 
established by the following considerations: 

SILICA. 

From the presence of quartz as the most abundant gangue mineral, we may 
safely infer that silica was present in the vein-forming solutions. Chemists gen¬ 
erally agree that silica exists in hot mineral waters as Si0 2 rather than as an acid or 
as an alkaline silicate. Moreover, the substance is believed to be present in a colloid 
solution. Colloids are supposed to exist in solutions as suspended particles and 
they exhibit certain striking differences from electrolytes in solution, especially in 
their mode of diffusion. They do not diffuse through semipermeable membranes 
or walls through which electrolytes, such as ordinary salts, may freely pass; on 
the other hand, electrolytes freely diffuse through colloid solutions and jellies, 
which may be considered as concentrated solutions of colloids. These facts help 
to explain the rare occurrence of silicification in the wall rocks of quartz veins, 
the colloid solutions of silica being held by the semipermeable rock walls, while 
other constituents and gases in solution may more or less freely permeate them. 

The derivation of the silica is a difficult matter to ascertain. One may conceive 
of its being dissolved by atmospheric waters from the granite, from the breccia, or 
from the various phonolitic rocks. The latter contain, however, extremely little 
free quartz, and almost the only way in which ascending waters could abstract 
silica from it would be by decomposition of the various silicates. Some of the 
silica in the waters has certainly this origin, but it by no means follows that this is 
the only source. It is quite possible that the phonolitic magma cooling at great 
depths, gave off some* silica, together with some of the magmatic water, which it 
may have contained. 


217 


218 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


FLUORIDES. 

The almost universal presence of fluorite in vein fillings and as a metasomatic 
product in the rocks shows that the solution contained fluorine. The general char¬ 
acter of the solution indicates the presence either of calcic fluoride or of alkaline 
fluorides. 

Fluorite is by no means insoluble in pure water. According to the experi¬ 
ments of Wilson,® 1 part of calcium fluoride is soluble in 26,923 parts of H 2 0 at 15° C. 
It is stated 6 that it is more soluble in waters containing C0 2 , although exact figures 
are not given. It is thus less soluble than gypsum, of which 1 part dissolves at 
ordinary temperature in about 420 parts H,0, but considerably more soluable than 
barium sulphate, of which, it is stated, that 1 part is soluble in 429,700 parts H 2 0 
at +18° C. 

Under the influence of solutions containing alkaline carbonates fluorite alters 
to calcite, and this process is believed to be more or less active in the oxidized zone 
wherever the absence of pyrite permits the waters to be of an alkaline character. 

Fluorspar heated at 100° or 150° C. with solutions of sodium carbonate is 
easily converted to calcium carbonate, while sodium fluoride goes into solution 
(Sorby). This reaction takes place both at the elevated temperatures mentioned 
and at ordinary temperatures. Superheated water attacks fluorite and hydro¬ 
fluoric acid is formed. 

It is known that fluorine is contained in many thermal springs. The list of 
waters containing these constituents would no doubt be greatly extended if careful 
search were made for the element. Owing, however, to certain analytical difficul¬ 
ties it is rarely looked for. Fluorine has been shown to exist in the hot springs of 
Carlsbad, Plombii'res, Contrexeville, Chatenois (Alsace), Vichy, and Bourbon- 
l’Archambault. One of the waters at Vichy contains 0.00769 g. fluorine per liter, 
and that of Bourbon-1'Archambault 0.002689 g. per liter. c 

The- springs at Carlsbad and at Plombieres are known to deposit fluorite in 
small quantities. The latter springs, in fact, ascended on an old system of fissure 
veins, the gangue of which consists chiefly of quartz and fluorite. Fluorite some¬ 
times occurs closely associated with volcanic eruptions and is known especially 
from the volcanoes of Campania, Italy. The tuffs in this region are said to contain 
large masses of fluorite, which have probably been formed by the reaction of volcanic 
emanations containing fluorine upon the fragments of limestone. 

The two most important reactions concerning the formation of fluorite estab¬ 
lished by Bischof d are (1) the above-mentioned decomposition of fluorite by alkaline 
carbonates with the formation of calcite and alkaline fluorides, and (2) the decom¬ 
position of sodium fluoride in solution at ordinary temperature by calcium silicate 
with the formation of calcium fluoride. Bischof showed that ordinary rocks like 
basalt or trachytes, which contain some calcium silicate, had a like effect, but in 
less degree than the artificial silicate of lime. 

o Wilson, George, On the extent to which fluoride of calcium is soluble in water at 60° F.: Kept. Twentieth Meeting 
Brit. Assoc. Adv. Sci., 1S50, pt. 2, p. 69. 

i> Nickh'S, J., Recherches sur la diffusion du floor: Anal, de Chimie, 3d ser., vol. 53, 1858, p. 437. 
c Daubree, A., Les eaux souterraines k lYpoque actuelle, vol. 2, Paris, 1887, p. 9. 
d Bischof, G., Chemische Geologie, vol. 1, 2d ed., Bonn, 1863, pp. 48 and 54. 




ORIGIN OF THE ORES. 


219 


Fluorite was first proved to exist in the spring deposits at Carlsbad by Berze¬ 
lius.® From bis experiments it is clear that waters may contain Si0 2 and CaF 2 , 
and that the two may be deposited together. Either of the two substances may 
be first deposited, and waters containing Si0 2 may subsequently dissolve the 
fluorite formed and replace it by quartz. According to Berzelius, the fluorite was 
dissolved as such in the waters of Carlsbad, which he says do not contain any sodium 
fluoride. The experiments of Bischof and Sorby would, however, show that the 
fluorine was present as sodium fluoride, for calcium fluoride and alkaline carbonates 
can not exist together in the same solution, and the Carlsbad waters contain a con¬ 
siderable amount of the latter salts. In mineral waters alkaline fluorides can, how¬ 
ever, exist together with calcium bicarbonate, as the two substances do not react. 
The testimony is somewhat conflicting, but it seems most likely that the waters of 
Cripple Creek contained sodium fluoride, and that the fluorite was separated by 
reaction of calcium silicate on the solutions. 

In tracing the origin of the fluorine we are first confronted by the fact that the 
Pikes Peak granite contains a certain small percentage of fluorite as a primary 
mineral/' in some cases, as in the Summit type, amounting to 0.55 per cent. In 
the vicinity of Cripple Creek no primary fluorite could be detected in the rock. 
However, if the fluorine were derived from the granite, we should expect secondary 
fluorite to be most common in this rock, which is certainly not the case in the dis¬ 
trict. Two or three miles south of Cripple Creek this granite does contain several 
small veins in which fluorite is associated with barite. The mineral is here either 
purple or green, the latter color never appearing in the deposits at Cripple Creek. 
It is very doubtful whether these veinlets really belong to the same class of deposits 
as those within the district proper. 

Another possibility is that the fluorine is leached from the volcanic rocks. No 
primary fluorite has, however, been observed in these and no definite traces of 
fluorine have been shown by the analyses. The presence of the mineral lovenite, 
if substantiated, would establish the presence of fluorine, but there seems to be some 
doubt regarding the identification (p. 65). As a third possibility, the fluorine, 
together with other volatile constituents, may have been given off by the phono- 
litic magmas on their consolidation at higher levels of the earth’s crust. We incline 
toward this view as the most probable explanation. There certainly exists a 
remarkable connection between phonolitic rocks and deposits containing fluorite 
and gold, exemplified not only at Cripple Creek, but also in the Black Hills, Judith 
Mountains, and Little Kocky Mountains/' 

CHLORIDES. 

The general distribution of sodalite in the Cripple Creek rocks indicates the 
presence of NaCl, and, in fact, the analyses of phonolites, latite-phonolites, and 
syenites show amounts of Cl up to 0.55 per cent. During the decomposition of this 
mineral by alkaline waters NaCl would be dissolved, and in this reaction is one 


aChemisehe Geoiogie, vol. 2, 2d ed., Bonn, 1864, p. 89. 

b Mathews, E. B., The granitic rocks of the Pikes Peak quadrangle: Jour. Geol., vol. 8, No. 3, April-May 1900, p. 237. 
cLindgren, W., Metasomatic processes in fissure veins: Trans. Am. Inst. Min. Eng., vol. 30, 1901, p. 657. 





220 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


source of chlorides in the waters. As chlorides are found among the volatile sub¬ 
stances emitted during eruptions, it seems most probable that the magma of any 
rock which now contains chlorine contained more of it before the pressure in the 
magma was reduced by movement to a higher level in the earth's crust, and that 
chlorine, mingled with magmatic water, was one of the constituents which escaped. 

SULPHATES. 

• That sulphates were present in the waters is indicated by the almost universal 
occurrence'of celestite or sulphate of strontium in the veins (pp. 124, 125), as well as 
by the more sparing development of barite. Celestite is fairly soluble in water, the 
proportions given varying from 6,895 to 10,101 parts of water (at 15° C.) for 1 part 
of celestite. It is, however, much more soluble in water containing sodium chloride, 
1 part of the sulphate dissolving in 457 parts of water with 15 per cent NaCl. rt 
Celestite is very much more soluble than barite, of which 1 part dissolves in 429,700 
parts of water. 

The presence of celestite rather than barite in the veins is a very unusual 
occurrence in mineral veins, although known in a few cases from France and Hun¬ 
gary. The granites and phonolites, as well as the basic dikes of Cripple Creek, 
contain a very small amount of baryta, varying from a trace up to 0.18 per cent, 
and practically only a trace of strontia, occasionally rising to 0.07 per cent. On 
the other hand, the majority of the latite-phonolites and the syenite are much richer 
in both constituents. Six analyses of these show from 0.13 to 0.24 per cent baryta 
(average of the six, 0.19 per cent BaO) and from 0.03 to 0.21 per cent strontia 
(average of the six, 0.12 per cent SrO). Strontia is here present in much larger 
quantities than is usual in rocks, and the proportion is exceeded only in certain 
leucite and analcite rocks, monchiquites, tinguaites, and sjrnites from Montana and 
Wyoming. 6 The average percentage of baryta in rocks, as calculated by Clarke, 
is 0.11 per cent baryta and 0.04 per cent strontia/ The latter figure is probably 
higher than the actual average. 

Strontia exists, moreover, in many thermal spring waters in amounts exceeding 
those of baryta. Salts of strontium are known from many spring deposits, such as 
Vichy, Carlsbad, and Hammam-Meskoutine, and celestite is deposited by the hot 
springs of Bourbon-1' Archambault/ From the data given there is, therefore, some 
reason to suppose that the strontia may have been leached from some of the intrusive 
rocks at Cripple Creek, but as celestite occurs in the veins throughout the district, 
irrespective of the particular wall rock, it follows that this leaching has probably 
not taken place within the zone opened by mining, but perhaps rather in intrusive 
latite-phonolite and syenite at greater depths. 

Calcium sulphate is not found as a primary constituent of the veins, but the peculiar 
occurrence of large masses of gypsum associated with pyrite and fluorite at the Deer- 
horn mine (p. 284) leads to the belief that waters rich in sulphates of the alkaline 
earths appeared as one of the latest phases of thermal activity. The closest analogy 

a See Comey’s Dictionary of Solubilities. 

b Clarke, F. W., Analyses of rocks: Bull. U. S. Geol. Survey No. 228, 1904. 

cOp. cit., p. 17. 

d Daubree, A., Les eaux souterraines a l’epoque actuelle, vol. 2, 1887, p. 18. 




ORIGIN OF THE ORES. 


221 


t 


to this would perhaps be found in the hot waters of the Comstock lode, which are 
exceptionally rich in these constituents. 

The phonolite, syenite, and latite-phonolite contain appreciable quantities of 
sulphuric acid combined in the mineral hauynite of those rocks. The maximum 
amount found is 0.37 per cent. As this mineral is very easily decomposed under the 
influence of vein-forming solutions with the formation of sericite, it is evident that 
the waters would carry away soluble sodium sulphate. This origin of a part of the 
sulphates in the water may be considered established, but it is probable that the 
magma brought up from great depths and cooling at a level still far below the present 
mine workings gave ofl part of its sulphur trioxide, which ascended, together with 
so much of the magmatic water as was set free. 

CARBONATES. 

The metasomatic processes clearly indicate that the waters contained carbon diox¬ 
ide, either as dissolved gas, as bicarbonates, or as normal carbonates of the alkalies. 
It has been shown that an active decomposition of silicates proceeded in the rock 
accessible to the vein solutions. This could be explained under any of the three sup¬ 
positions, but the most plausible view seems to be that bicarbonates and an excess of 
carbon dioxide were present. The processes outlined indicate distinctly that sodium 
was carried away as a carbonate and that the waters gradually became more charged 
with this substance on their upward journey. The metasomatic processes observed 
also suggest that the waters originally contained more potassium, which gradually 
was substituted for the sodium in the rocks. 

No adequate explanation is available for the occurrence of C0 2 in the waters on 
the supposition that they were ascending surface waters. It can not have been 
leached from the volcanic rocks nor from the granitic rocks, since neither contain 
carbon dioxide or carbonates/' 

Inasmuch as all cooling volcanic rocks give off carbon dioxide and as emanations 
of this kind are abundant in the district to-day, it appears certain to us that the 
carbonates in the veins and in the altered rocks of Cripple Creek were formed from 
the carbon dioxide exhaled by crystallizing magmas. 

HYDROCARBONS. 

The purple color of the fluorite of Cripple Creek is very characteristic and often 
very intense; in thin sections parts of a crystal may be almost opaque, but the color 
is very irregularly distributed. Wyrouboff and Von Lasaulx have shown that this 
color is due to a hydrocarbon, and thus we may conclude that the waters contained 
some of this substance, the derivation of which must remain problematical. Possi¬ 
bly it is derived from the small quantities of bituminous coal occasionally found in 
the breccia. Hydrocarbons are by no means entirely unknown in mineral veins, the 
quicksilver deposits offering one conspicuous example. 

a The supposed derivation of carbon dioxide from fluid inclusions in the granite is altogether improbable; moreover, the 
explanation is quantitatively insufficient. Inclusions of carbon dioxide in granite-quartz are of comparatively rare occur¬ 
rence. Aqueous solutions assuredly predominate. 

13001 — No. 54—06 - 16 




222 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

HYDROGEN SULPHIDE. 

The abundance of pyrite, which without notable addition of iron has been 
found throughout the rocks affected by the solutions, shows that hydrogen sulphide 
or sodium sulphide, or both, must have acted on the iron oxides and silicates. This 
is amply confirmed by microscopic examination. The widespread pyritization, indi¬ 
cating great capacity for diffusion on the part of the sulphur-bearing compound, 
would indicate that H 2 S as a gas dissolved in water was the chief reagent. But if 
sodium carbonates were present sodium sulphydrate would form;" this, by heating 
or by the presence of certain metallic sulphides, may partly change to Xa 2 S, so that 
it is quite possible that both substances were active. 

Neither the granitic nor the phonolitic rocks are knowm to contain sulphides 
which could have jdelded the necessary sulphur. Hydrogen sulphide might, of course, 
have formed by the reduction of sulphates by organic matter; but very large quan¬ 
tities of sulphur compounds were evidently active at Cripple Creek, and here also 
w T e would attribute the sulphur to emanations from cooling intrusive magmas. This 
position is strengthened by the fact that sulphur in various forms is usually given 
off during eruptions of lavas at the surface. 

IRON. 

It has already been pointed out that the quantity of pyrite in the veins is very 
small. In the ores this mineral rarely exceeds 5 per cent. (See analyses, p. 172.) 
Most of this pyrite is contained in the altered country rock, which in mining can not 
be separated from the tellurides and quartz of the fissure filling. The iron in this 
pyrite is almost wholly derived from the original iron silicates in the rock. Probably 
less than 10 per cent of the pyrites in the ores was deposited in the filling of the 
fissures. We arrive thus at the conclusion that the solutions contained very little 
iron in a condition to form pyrite. 

CALCIUM AND MAGNESIUM. 

Dolomitic carbonates are of widespread occurrence in the altered rocks, but are 
nowhere present under conditions suggesting an introduction of either of these metals. 
The silicates of calcium and magnesium are simply converted into carbonates, and 
in some cases the percentage of the former metal is notably decreased, giving evi¬ 
dence of a partial leaching by the vein-forming waters. It is a noteworthy fact 
that the mines situated in areas of syenite and latite-plionolite, the rocks in which 
lime is most abundantly present, contain the largest amounts of dolomitic carbonates, 
both in the altered rocks and as filling of seams. There is thus strong evidence that 
the lime and magnesia contained in the v T ater were, to a large extent, at least, 
derived from the surrounding country rock. As the waters contained carbondiox- 
ide, the metals must have been present chiefly as bicarbonates. 

ALKALI METALS. 

The substitution of potassium for sodium in the newly formed silicates suggests 
that the waters were originally richer in the former metal, but this can not be said 


o Becker, G. F., Geology of the quicksilver deposits of the Pacific slope: Mon. U. S. Geol. Survey, vol. 13, 1S88, p. 427. 




ORIGIN OF THE ORES. 


223 


to be definitely established. It is certain that sodium was extracted and that the 
waters must have been greatly enriched in this metal during their journey through 
the rocks. The alkalies were present as chlorides, carbonates, sulphates, and sul¬ 
phides, as well as their several ions. 

TELLURIUM AND GOLD. 

% 

If it be assumed that the ores shipped average $40 per ton, it should be remem¬ 
bered that the actual ore, which in the fissure deposits of Cripple Creek is formed 
only in the narrow seams and cracks of the lode, constitutes less than 10 per cent, 
perhaps only 5 per cent, of the total material extracted, and that it would thus 
have a value of upward of $400 per ton. For present purposes we may assume 
that this material consists of 60 per cent quartz, 20 per cent dolomite, and 20 per 
cent fluorite, to which should be added 0.1 per cent gold and 0.2 per cent tellurium, 
besides small amounts of iron, copper, lead, zinc, and molybdenum, each of which 
would on the average rarely exceed a fraction of 1 per cent. A water depositing 
such a product was surely of a most unusual character, compared to ordinary 
surface waters, and even compared to those which deposited the normal gold-quartz 
veins, in which the tenor of the filling is rarely higher than 1 ounce per ton. 

Concerning the reactions by which the tellurides were deposited or the con¬ 
dition in which they existed in the solution our information is scant. The associa¬ 
tion of tellurides with fluorite is an interesting but probably not at all essential 
point, because, as Penrose has already emphasized, there is no quantitative relation 
between the two minerals. In some of the richest ores fluorite may be extremely 
scarce. In his great monograph on metamorphism, Van Hise“ devotes consider¬ 
able space to a discussion of the tellurides. He says: 

At first thought one might conclude that the gold, silver, and tellurium were transported as tellurides 
and deposited as such without chemical change, but the recent work of Lenher and Halit is decidedly against 
this view. They have found no solvent whatever for tellurides of gold without breaking up these compounds 
and producing salts of tellurium, the gold usually being left in the metallic form. Moreover, as has already 
been noted, they have shown that metallic tellurium and seven of the more common mineral tellurides of 
gold and silver rapidly reduce gold from its solutions, forming metallic gold, the tellurium at the same time 
going into solution. Further, they have proved that the presence of any of the soluble tellurides, including 
hydrogen tellurides, is sufficient not only to throw the gold out of solution, but to prevent it from getting 
into solution. Other soluble salts, where tellurium acts as an acid, are the tellurites and tellurates. Tellurous 
oxide or acid is also sparingly soluble. All of these compounds, like tellurides, precipitate gold from its solu¬ 
tions in a metallic form, not as telluride. From the foregoing it appears that if tellurium compounds in which 
tellurium is a part of the acid are essential for the formation of the tellurides of gold, these tellurium salts and 
the gold have come into the trunk channel from separate sources. They could not have traveled together; 
else the gold would have been thrown from the solutions before reaching the trunk channels. 

* ****** 

It may be that the key to the problem of the deposition of the tellurides lies in their association with 
sulphides. We have already seen that telluric salts of the type of TeCl 4 may travel with gold in solutions. 
It has already been pointed out that gold, in most cases, probably also travels as a chloride, and thus solutions 
of auric chloride and telluric chloride, may together enter trunk channels which contain sulphides. In such 
trunk channels the reaction of the sulphides might reduce both the gold and the tellurium simultaneously 
and thus produce tellurides of gold; or, by the reaction of the sulphides upon the telluric salts, these may 

a Mon. U. S. Geol. Survey, vol. 47, 1S04, pp. 1119-1125, especially pp. 1120, 112:. 

6 Lenher, Victor, Naturally occuring telluride of gold: Jour. Am. Chem. Soc., vol. 24, 1902, pp. 35.5-360. Hall, R. D., 
and Lenher, Victor, Action of tellurium and selenium on gold and silver salts: Idem, pp. 918-927. 




224 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


be reduced to tellurous salts, which, as already explained, would decompose into metallic tellurium and telluric 
salts, and the tellurium would precipitate the gold. Under these or some other conditions, the gold and 
tellurium go down together, with a definite composition, and thus form the tellurides. 

We are not able to agree with these conclusions; on the contrary, we think 
the evidence from the general occurrence is very strong that gold and tellurium 
existed together in the solutions, and, with the assistance of Dr. W. F. Hillebrand, 
we have been able to show that they do so exist in a combination of two solvents 
which are believed to have been contained in the alkaline vein-forming solutions— 
i. e., sodium sulphide and sodium carbonate. 

Doctor Hillebrand sums up his experiments as follows: 

The first attempts with bicarbonate of soda solution at ordinary temperatures led to the erroneous conclu¬ 
sion that this solvent exerted an appreciable action upon the telluride. It was found, however, that the tel¬ 
lurium going into the,solution undoubtedly came from a coating of tellurite upon the calaverite grains, for subse¬ 
quent treatment of this same powder with the bicarbonate solution gave entirely negative results. That 
such a coating existed upon the calaverite grains was rendered further evident by the fact that a first treat¬ 
ment with hydrochloric acid showed tellurium in solution, while subsequent treatments of the same powder 
gave negative results. A further experiment with bicarbonate solution on calaverite powder thus purified 
was made by sealing mineral and solution in a glass tube, after expelling the air by a current of carbon 
dioxide. The tube was then heated to 150° for many hours. When opened and the powder separated from 
the solution by filtration, no tellurium whatever could be detected in the filtrate. 

The case was quite dilferent, however, if, instead of the bicarbonate solution, one saturated to a greater 
or less extent with hydrogen sulphide was employed. Under these conditions it was a matter of ease to detect 
tellurium, as well as gold, in the filtrates, even after only one or two hours’ exposure at room temperature 
with exclusion of air. It was found possible to estimate quantitatively, with a fair approach to accuracy, 
both the tellurium and the gold. The amounts thus found accorded fairly well with the preparations in 
which these two elements combine to form the mineral calaverite. The absolute amounts were, in one case, 
for tellurium, 0.0011 g., for gold, 0.0008 g. The amount of calaverite which furnished the above quantities 
of tellurium and gold to the alkaline solution was approximately 0.4 g. in a moderately coarse state of division. 

As to the actual conditions existing in these solutions of calaverite, we are 
still in the dark; doubtless a partial dissociation has taken place, as in most electro¬ 
lytes, but we incline to the belief that the tellurides were dissolved as such and 
precipitated by supersaturation due to various physical changes. The synthesis of 
the tellurides offers a fruitful field of investigation which circumstances have not 
allowed us to enter. 

Concerning the derivation of the gold telluride we confess to a lack of con¬ 
clusive evidence. It may have been leached from the granitic rocks or from the 
volcanic rocks bj r ascending surface waters, or it may have been separated as 
exhalations from cooling intrusive magmas and brought up by ascending surface 
waters or by magmatic water. That it was leached from granitic rocks by surface 
waters is exceedingly improbable, for this hypothesis furnishes no explanation of 
the confinement of the deposits to the volcanic area. Whether the volcanic rocks 
now contain gold and tellurium, and if so, whether the surface waters would be 
able to extract them, we can not say. Determinations of gold in the volcanic 
rocks now accessible on the surface or in the mines would have little value, owing 
to the general permeation by solutions that has taken place and to the fact that 
an almost invisible seam in the rock might contain enough telluride to vitiate the 
result. Considerations concerning the quantitative relations of the sulphides and 


ORIGIN OF THE ORES. 


225 


the tellurides, as well as concerning the water circulation, make the derivation by 
leaching seem improbable (p. 224), and we therefore fall back upon the third alter¬ 
native, namely, to consider the gold, the tellurium, and perhaps the other rarer 
sulphides as emanations from a cooling magma under the influence of diminishing 
pressure. 

RELATIVE QUANTITY OF SULPHIDES. 

Little is to be said of the various sulphides and sulphosalts, except that they 
must have been present in the water and that according to the experiments of 
Becker" and Doelter 6 they were probably dissolved as sulphides in sodium sul¬ 
phide. Among them are sphalerite, galena, stibnite, tetrahedrite, and molybdenite, 
corresponding to zinc, lead, copper, antimony, and molybdenum. Zinc is on the 
whole most abundant, but the proportion does not appear to rise in many cases 
above 0.75 per cent and in places the metal is entirely absent. The other elements 
occur on the average only in minimal amounts, rarely rising above 0.1 per cent 
and more commonly about 0.02 per cent or 0.01 per cent. The quantity of tel¬ 
lurium and even of gold is often found to exceed that of these metals. A solution 
may of course contain sulphides and tellurides without their being precipitated. 
It is assumed that the precipitation is due to slowly changing physical conditions. 
But as the necessary requirement for precipitation is supersaturation, and as some 
of each sulphide has been precipitated, it is reasonable to conclude that the 3 r were 
precipitated in proportion as they were abundant in the solution. Such a pro¬ 
portion, however, if the metals have been leached from the volcanic rocks by 
atmospheric waters, would be highly remarkable. It would indicate that the 
waters contained as much molybdenum as copper and more tellurium than either. 
The average amount of iron deposited as sulphide in open spaces is but slightly 
larger than the tellurium deposited as tellurides. If these elements had been 
gathered by leaching we would be justified in concluding that .they existed in 
approximately similar proportions in the rock from which they were obtained. 
This may be looked upon as a reductio ad absurdum. 

Xo such difficulties appear when the metals are regarded as sulphide exhala¬ 
tions from cooling magmas, for here we have no separation according to solubility 
in water, but only according to the ability of a magma to hold certain substances 
in solution under rapidly changing physical conditions. That rare elements can 
be concentrated by this process is well shown by many pegmatite dikes. 


CONCLUSIONS. 


The waters which deposited the Cripple Creek veins were alkaline solutions 
containing the following compounds and ions, either free or in various combinations: 
SiO,, CO,, H 2 S, C0 3 , SO,, S, Cl, F, Fe, Sb, Mo, V, W, Te, Au, Ag, Cu, Zn, Pb, Ba, 
Sr, Ca, Mg, Na, and K. We believe that at least some of the Si0 2 , SO,, Cl, Fe, 
Ba, Sr, Ca, Mg, Xa, and K, are derived from the volcanic rocks by leaching of 
waters, while the remaining metals, as well as C0 2 , H 2 S, S, and some Si0 2 , Cl, and 
Iv were more probably separated from intrusive cooling magmas at considerable 
depth, and brought up as solutions in magmatic water given off in the same manner. 


a Mon. U. S. Geol. Survey, vol. 13, 1888, chap. 15. 


b Tschermaks Min. u. petrogr. Mittheilungen, vol. 2, 1889, p. 319. 




226 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


DEPTH AT WHICH DEPOSITION TOOK PLACE. 

The ores were deposited in the fissures of a volcanic mountain. Near its present 
highest point, with an elevation of 10,800 feet above the sea, the ore has been proved 
from the surface to a depth of 1,600 feet, and near the southern base of the volcanic 
lulls, with an elevation of 9,700 feet, it has been followed to a depth of 1,200 feet—in 
each case without notable change in quality but with a distinct decrease in quantity 
(p. 214). From physiographic considerations (p. 38) it is probable that the volcanic 
mountain had an unsymmetrical conical shape and that near the highest points of 
the present time a minimum of 1,000 feet of rocks covered the present outcrops. 
It is further probable that near the southern base the vein croppings of to-day 
were buried at least 500 feet deep. It is concluded that the ores which we see now 
were deposited at moderate depths ranging from a few hundred feet below the old 
surface to a maximum of about 3,000 feet. The occurrence of carbonized tree 
trunks at many places in the breccia (p. 31) tends to confirm this conclusion. 

TEMPERATURE OF THE SOLUTIONS. 

As the solutions moved within a volcanic cone, shortly after the end of the erup¬ 
tions, and as, being heavily charged with silica, carbon dioxide, and hydrogen 
sulphide, they actively deposited material and energetically altered the country 
rock, it follows that they were in all probability hot solutions. The similarity of 
the deposits to those formed by many hot springs emerging at the surface lends 
additional support to this conclusion. The most direct proof is furnished by aqueous 
inclusions in the quartz deposited. In addition to a gas bubble these very often 
contain solid material forming transparent adhesions to the walls of the cavity, 
but evidently once dissolved in the water. No inclusions of carbon dioxide have 
been found. 

On the other hand, the temperature and pressure at which the veins were 
formed were not very high, as shown by the fact that carbonates crystallize freely 
in the rock by replacement and in the fissures by crustification and also by the 
general absence of minerals like biotite, garnet, and pyroxenes, which are apt to 
form during conditions of high temperature and pressure from aqueous solutions. 
The critical point of water ( + 364 C. and 200 atmospheres) was probably not reached. 
We are inclined to believe that the temperatures ranged from + 100° C. to +200° C. 
and the hydrostatic pressure up to 100 atmospheres—that is, for the portions of the 
veins now accessible. 

TIME OF DEPOSITION. 

The ores were formed later than the latest actual eruptions; that is, later 
than the basic dikes. These dikes had solidified and had cooled at least to such 
degree that carbonates could form in them. Although the basic dikes to some 
degree followed the prevailing directions of the fissure system, the latter was not 
formed until after their intrusion. As the paths were opened they were filled bv 
depositing solutions. The filling being in many cases only partial, we may infer 
that the solutions circulated for a limited time only. 

That the veins are not recent is indicated by the formation of considerable 
placer deposits and by the depth and extent of subsequent oxidation. If we assign 


ORIGIN OF THE ORES. 


227 


a late Tertiary age to the close of direct volcanic activity, there is some reason for 
believing that the ore-forming epoch belonged to the close of that period. 

SOURCE OF THE WATER. 

The ore-depositing water was derived either from the atmosphere or from 
magmas under diminishing pressure and temperature or from both of these sources. 
In other words, it may have been a part of the ground water descending through the 
pores and fissures of the rocks from the surface on which it once fell as rain or snow, 
and possibly ascending, charged with dissolved material, from the lowest levels 
reached under the driving force of the volcanic heat encountered there. Or it may 
have formed part of the original molten phonolitic rocks and may have escaped 
from its bond during the ascent of this molten rock to levels of less temperature and 
pressure. Both hypotheses are plausible, though at first glance the former view 
seems much more natural and simple. Either may be difficult to prove, but it may 
be profitable to consider the probabilities involved. 

It will be shown in Chapter XII that the conditions of underground drainage 
are unusual. The porous, shattered volcanic mass is deeply sunk in much more 
massive and impervious granite and metamorphic rocks. It therefore holds water 
much as would a sponge in a cup. The circulation of 'the ground water in this 
volcanic plug is exceedingly slow; in fact, the«water is practically stagnant. The 
cold dilute sulphate solutions which constitute the ground water are evidently 
wholly impotent to deposit ores like those in the veins or to cause abundant pyritiza- 
tion of the rocks. They fill many open fissures in the rocks, but nowhere have they 
given the least indication of depositing telluride ores. 

If surface waters were present they must have constituted currents under- the 
influence of the heat of the volcanic rocks. This circulation was only a temporary 
phase, ceasing when the rocks had cooled sufficiently. 

Such waters ascending vigorous^ throughout the volcanic mass could not 
reasonably have been derived from the very limited surface area of that mass itself. 
They must have been derived chiefly from the surrounding granitic plateau. 
They must have percolated through the granite to great depths near the volcanic 
mass, and finally have been driven up by the volcanic heat still existing in it. 
Considering, however, the almost impermeable character of the granite, as demon¬ 
strated by the mining operations, it becomes very difficult, if not impossible, to 
conceive how a ‘sufficient amount of water could penetrate the porous volcanic 
mass from the surrounding granite to give rise to the strong ascending current 
which evidently streamed upward in every available fissure in this old volcano. 

The second hypothesis of the derivation of the vein-forming waters is that 
they were originally an integral part of the intrusive phonolitic magmas and were 
given off by release of pressure or by cooling and crystallization after the magma 
had ascended to higher levels. 

According to the general laws of solutions, pressure increases the solubility of 
water in magmas, and conversely, if all magmas contain more or less water which 
is just as much a part of them as is the silica, for instance, it follows that a portion 
of the water will be given off during the eruption. 


228 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


The volcanic rocks of Cripple Creek are rich in combined water. The average 
of the analyses shows 1.62 per cent combined water given off above + 110° C., and 
they range from 0.69 to 2.09 per cent. To a large extent this is contained in 
analcite, the primary nature of which is proved. Some of the phonolites contain 15 
per cent of this analcite and the latite-phonolites average 4.6 per cent. To a smaller 
extent the water is present in kaolin or other secondary hydrous minerals. It is 
assuredly not an exaggeration to say that the rocks contain an average of 1 per cent 
of combined primary water. The presence of primary water being firmly estab¬ 
lished, it follows, if the statement in the preceding paragraph is true, that the magma 
contained much more of it at greater depths. The water lost as steam by the intru¬ 
sive bodies under our present range of observation doubtless partly permeated the 
rocks and was partly dissipated in the air at the time of the eruption. But unques¬ 
tionably there are large intrusive masses which did not attain the level of those 
now visible, though they rose to much higher levels than they originally occupied. 
Their water was probably partly expelled from the cooling mass, but was held in its 
confines under strong pressure, having abundant opportunity to dissolve the other 
substances which may have emanated from the magma. As the volcanic mountain 
settled down deep fissures were created, which reached to the levels of these stored 
hot waters and afforded them means of escaping toward the surface. Such is the 
explanation of ore deposition by “magmatic” or “juvenile” waters, to follow 
Suess’s terminology, and to these we are inclined to attribute the largest share of 
ore deposition, possibly the whole. The storage reservoir was limited, and the 
supply of these strange solutions was soon exhausted. Surface waters followed 
the retreating juvenile waters and filled the “sponge in the cup” until equilibrium 
was established. At the present time the volcano appears extinct, and yet a few 
hundred or a thousand feet below the surface the faint exhalation of carbon 
dioxide and nitrogen are met—the last volatile products of the phonolitic magmas. 

MODE OF DEPOSITION. 

The laws governing the actual deposition of materials in mineral veins are little 
known, and it must be confessed with regret that the last ten years have not seen 
much direct advancement, although the foundations for it have been laid broad 
and deep by the development of physical chemistry. We have reached a point 
where further progress depends on experimental work with solutions at high tem¬ 
perature and pressure. , , 

If an alkaline solution, such as is indicated above (p. 224), with an unascertained 
state of ionization, ascends in fissures through porous volcanic rocks, a most com¬ 
plicated set of reactions will follow. Pressure and temperature will constantly 
change, certain compounds will be precipitated, and constant changes in the com¬ 
position of the solution will take place. It is further to be considered that the 
solutes 0 or some of them may diffuse through the walls and that different ions may 
diffuse at various rates. It is even possible that the walls in places maj" act as 
semipermeable membranes which will allow not any solutes to pass. There is also 
the chemical action of the solutions on the porous rocks, with attendant loss of 

a Solute in physical chemistry means the substance dissolved; solvent indicates the medium in which the substance is 
dissolved. 




ORIGIN OF THE ORES. 


229 


some constituents and gain of new ones, and finally the mingling of the ascending 
solutions with the moisture already permeating the rock. The most satisfactory" 
way of attacking such a problem is to begin by experiments in which these confusing 
complications are to some extent eliminated. 

Simply from the results as we see them, without positive knowledge as to the 
composition and physical conditions of the solutions, a few conclusions may be 
reached. One of the most striking facts is the difference in composition between 
the filled veinlets and the altered country rock. The silica, the gold tellurides, 
and the sulphides (except pyrite) are retained in these fissures and precipitated in 
them. The walls are evidently not as a rule permeable for these substances. It 
seems to be generally true that in gold-quartz veins the silica, the gold, and some 
sulphides, such as galena, sphalerite, and chalcopyrite, are always deposited in open 
spaces, if such spaces are available. This rule, which may not be without exceptions, 
indicates that the wall rocks effect a separation in the solutions and that the sub¬ 
stances mentioned penetrate them less easily than the other constituents of the solu¬ 
tions. For tellurides the rule is not inflexible, for it has been shown that they also 
occur in metasomatic form. In the “granite ore/’ however, which is considered 
one of the best examples of metasomatic deposition of tellurides, most of the latter 
are probably deposited in cavities created by the solutions and consequently not, 
strictly speaking, metasomatic. It is known that tellurides in undoubted metaso¬ 
matic development occur abundantly in Kalgoorlie, Western Australia. 

This question of diffusion through porous rocks in relation to veins was first 
suggested by a microscopic study of the quicksilver ore? of California and of the 
altered wall rocks of gold-quartz veins in the same State. 

G. F. Becker" first expressed the belief that a law existed governing this phe¬ 
nomenon and wrote as follows: 

Osmotic hypothesis .—These observations would be explained if it were true in general that liquids mil 
penetrate a dense wall or septum at a sensible rate only when there is a chemico-phy ical reaction between 
the solid and the fluid. Here the term chemico-physical reaction is intended to express any chemical union 
or physical change attended by the evolution of heat, or rather by the degradation of energy. There is reason 
to think that such a law really exists, though it can not be said that it is conclusively proved. * * * 

On this hypothesis the concentration of ores in deposits would be largely due to the fact of the lack of 
action between their solutions and the wall rocks; and the decomposition of the country rock, so often observed 
near veins, would be due to the absorption of solutions of gangue minerals by the walls. In short, there would 
be a species of concentration by dialysis. 

As expressed by Becker the hypothesis is probably not true, for it is known 
that solutes diffuse through chemically inactive membranes or porous bodies at 
varying rates; some are entirely impermeable while others are partly so, and the 
local osmotic pressure varies according to this permeability. But it is probably 
true that the rate of diffusion partly depends on chemical action between mem¬ 
brane and solute. The silica was in all probability contained in the waters in 
colloidal, easily soluble form, 6 and it is at least a legitimate subject for inquiry 
whether or not the sulphides and tellurides were dissolved in the same manner. 

a Quicksilver ore deposits: Mineral Resources IT. S. for 1892, U. S. Geol. Survey, 1893, p. 156. 

b Lindgren, W., Gold-quartz veins of Nevada City and Grass Valley, Cal.: Seventeenth Ann. Rept. U. S. Geol. Survey 
pt. 2, 1896, p. 183. 


/ 










230 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

It is well known that various sulphides of the metals, as well as some of the 
metals themselves—particularly gold—can exist as colloid suspensions.Electric 
currents in acidulated water through gold electrodes easily produce red clouds of 
colloidal gold in the liquid. 6 Under certain conditions hydrogen sulphide may 
produce colloidal suspensions of sulphides instead of precipitates, and these again 
may be coagulated by the addition in sufficient amounts of an electrolyte, such as 
a chloride. On the other hand, the presence in fairly small quantity of a gelatin¬ 
izing colloid in a liquid may prevent this coagulation of colloidal suspensions by 
salts. How far crystals can be produced from such a colloidal solution or suspen¬ 
sion is not certain, but that quartz can and does crystallize from them seems fairly 
well established by observation on siliceous springs. Recent experiments also 
show that in a solution containing a colloid and an electrolyte, crystals can form 
which contain both substances. 0 

Colloid solutions diffuse with the utmost difficulty and are easily retained by 
porous walls or by other colloids, while crystallized substances (crystalloids) diffuse 
as easily through colloidal masses as through water.' 7 

It is possible to separate mixtures of colloids and crystalloids by diffusion 
through colloidal walls. Such a separation has undoubtedly taken place in the fis¬ 
sures. If we suppose a concentrated solution adjoining a weak one or adjoining 
pure water, diffusion will take place into the latter. Should the two solutions be 
separated by a semipermeable wall which wholly or partly prevents the transmis¬ 
sion of the solute, osmotic conditions will result and the surrounding water will wan¬ 
der into the concentrated solution and dilute the same. Such a condition of affairs 
might easily exist in certain veins. 

Diffusion in itself is a slow process, and yet in porous rocks may well play an 
important role, especially when chemical action accompanies it. In the latter case 
adsorption and metasomatism cause constantly changing conditions of saturation 
by which the process is made enormously complicated. As an evidence of this we 
refer to the chapter on metasomatic action (pp. 184-195), in which it is shown that 
pyritization, carbonatization, and the formation of sericite and adularia often vary 
quantitatively in the same rocks to a degree which renders it impossible to believe 
that the solutions could have preserved the same composition throughout. 

During the alteration of the country rock, sulphur, carbon dioxide, fluorine, 
and possibly also potassium, are the chief elements introduced, and in exchange 
sodium, with a little silica and lime, have been carried away. Quantitatively the 
most prominent newly fdrmed minerals are pyrite and dolomitic carbonates, and this 
suggests the question whether practically all of the pyritization and carbonatization 
in the country rock could not have been effected by means of H 2 S and C0 2 , dissolved 
in the waters. The diffusion of dissolved gases is governed by the same laws as is 
that of dissolved liquids or solids. In general the diffusion constant is smaller for 
bodies of higher molecular weights. Consequently we should expect, for instance, 

a Noyes, Arthur A., The preparation and properties of colloidal mixtures: Jour. Am. Chem. Soc., vol. 27, No. 2, February, 
1905, pp. 85-104. 

b Bredig, G., Anorganisehe Fermente: Darstellung kolloidaler Metalle auf electrische Wege und Untersuchung ihrer 
Katalytischen Eigenschaften, Leipzig, 1901. Cited by Noyes, loc. cit., p. 95. 
cVan Bemmelen, J. M., Zeitschr. f. anorgan. Chemie, vol. 36, 1903, p. 393. 
d Ostwald, W., Grundriss der allgemeinen Chemie, Leipzig, 1899, p. 197. 






FUTURE OF THE DISTRICT. 


231 


a solution of hydrogen sulphide to permeate the rocks with more ease than a solution 
of salts of the heavy metals. The same applies in a less degree to carbon dioxide 
and to the ordinary alkaline salts. Hydrolysis of many salts of the heavy metals 
has a tendency to transform the bases into colloid solutions or suspensions, and for 
this reason also such substances are more apt to remain in the fissures. Fluorite 
is common in the altered rocks, but only in very small amounts, indicating that 
diffusion of alkaline fluorides has taken place. 

In general, then, the acids will permeate the rock more extensively than the 
bases and, as Van Hise says,° “in underground solutions the alkalies and alkaline 
earths, with the exception of magnesia, will largely take possession of the acids. To 
a less extent this is true of magnesia and to a still smaller degree of alumina and 
iron. Thus we have the partial explanation of the relative solubility of the bases. 
The alkalies are dissolved to the greatest extent; next in order comes lime, then 
magnesia, and finally iron and alumina.” 

It is not denied that solutions of heavy metals may freely permeate many 
porous rocks—there are, of course, many degrees of porosity—but they will not do 
so if open fissures are available and if there is no very strongly pronounced chemical 
reaction between the rock and the solution. How conditions may change in this 
case is well shown by the energetic metasomatic action of lead solutions on limestone. 

We believe that the waters ascended in the deeper part of the volcano with 
comparatively great velocity on the fewer fissures and in the smaller areal space 
there available. Nearing the surface it spread through a much larger space in a 
more complicated fissure system. The speed of the current became checked; in 
places conditions no doubt approached stagnation; locally the solutions even 
became descending instead of rising; deposition and chemical action on the country 
rock changed their composition; and mingling with fresh ascending waters, possibly 
also with atmospheric waters, induced further precipitation. In this manner we 
would account for the smaller amount of ores deposited in depth and the richness 
and abundance of ore nearer to the old surface. The portion of the volcano 
removed by erosion may have contained still richer deposits. 

FUTURE OF THE DISTRICT. 

To predjct the future yield of any mining district is no easy task; the conditions 
under which most ores are deposited are as yet too imperfectly understood and the 
deposits themselves are usually too erratic in form and distribution to give certitude 
to such predictions, even when these are based upon a careful study of the history 
and present condition of a district. Nevertheless, it is part of the duty of the geolo¬ 
gists who have officially investigated the Cripple Creek district to interpret to the 
best of their ability the bearing of ascertained facts upon future mining develop¬ 
ment. For such a forecast of the future moderate probability is all that can be 
claimed. 

As has been pointed out in the preceding pages, the largest known ore bodies 
of the district are apparently confined within a zone which extends from the surface 
to a depth of 1,000 feet. In general, explorations below that depth have been much 
less satisfactory as regards quantity of ore than explorations above. It is certainly 


a A treatise on metamorphism: Mon. U. S. Geoi. Survey, vol. 47, 1904, p. 92. 





232 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


true that some large ore bodies as yet show no sign of depletion in depth, and that 
some good pay shoots have been found at a depth of 1,400 to 1,500 feet. On the 
other hand, the number of ore shoots that have been exhausted with increase in 
depth is considerable. 

It is probable that the ore bodies, known or unknown, occurring below the 
1,000-foot zone are neither so large nor so abundant as those nearer the surface. 
The discovery and exploitation of these deeper ore bodies is, moreover, beset with 
increasing difficulties, chief among which is the problem of dealing with the under¬ 
ground water. For these reasons it is unlikely that the zone between the 1,000-foot 
and 2,000-foot levels will yield as much as the zone between the surface and the 
1,000-foot level, but it is probable that some strong fissures may carry payable ore 
to far greater depths than those yet attained. 

As regards the zone above the 1,000-foot or 1,500-foot level, it is well to bear in 
mind that it still contains much ore, both as parts of known ore shoots and as yet 
undiscovered ore bodies. It is certain that many of these undeveloped ore bodies 
will be mined in the near future and that this zone will contribute the most 
important part of the production. 

It is probable that the production of the district, while exhibiting fluctuations, 
will, on the whole, slowly decline. New ore bodies will undoubtedly be discovered 
from time to time, and individual mines may be as profitable in the future as they 
have been in the past, or even more so. An increased output may be expected to 
follow each successful step in deep drainage. But existing conditions indicate 
that if the maximum production of $18,000,000, in 1900, is to be surpassed, the 
increase will be due to the ore bodies encountered in the upper zone. 




r 


CHAPTER XII—UNDERGROUND WATER. 


INTRODUCTION. 

The mode of occurrence of the underground water in the Cripple Creek district 
presents some unusual features, and has been the subject of special reports to the 
Portland company by Messrs. Victor G. Hills and Charles J. Moore and of a report 
to the Elkton company by Mr. Seeley W. Mudd. rt With the common conclusion 
of these engineers, that the underground water of Cripple Creek is essentially 
stored water, we are in full accord. We are also indebted to them as well as to 
Messrs. Countryman & Jaquith, engineers of the El Paso tunnel, and to Mr. Sher¬ 
wood Aldrich, of the Elkton Mining Company, for many facts pertaining to the 
water history of the mines and tunnels. 

ORIGINAL WATER SURFACE. 

The annual precipitation in the district is moderate. According to figures 
furnished by the Weather Bureau, it was 13.55 inches in 1903 and 24.01 inches in 
1904 (an unusually wet year). As these are the only years during which a record 
has been kept, a close estimate of the average annual precipitation can not be made. 
The precipitation, however, is certainly less than on Pikes Peak, where observa¬ 
tions extending over a period of fifteen years show an average of 28.65 inches. 
The average for Cripple Creek is probably not far from 16 inches. The slopes in 
the Cripple Creek district are, for the most part, bare, are frequently swept by 
dry winds, and are fairly steep, so that a considerable proportion of the rain and 
snow is evaporated or runs off without sinking into the ground. Finally, the dis¬ 
trict is deeply dissected by streams, and. as a whole, stands high above neighboring 
valleys. There are thus present conditions suggesting at first glance unusual depth 
of ground-water surface. 

Such, however, is not the case. The deep shafts in the main volcanic neck, 
where the ground had not been previously drained by neighboring workings, 
encountered water at moderate depths. As the shafts of the district did not reach 
water simultaneously, it is evident that the record of “'first water,” as a means of 
determining the original form and position of the ground-water surface, is of unequal 
value in different mines. According to Mr. V. G. Hills, who has for several years 
carefully collected and studied the available facts bearing upon the underground 
water, the only mines whose records of "first water” are useful in this connection 

a For the reports of Messrs. Hills and Moore, see Ninth Ann. Rept. Portland Gold Mining Company, J903. See, also, 
Hills, V. G., Water in the mines of Cripple Creek: Eng. and Min. Jour., vol. 76, 1903, pp. 117 (table), 195-197. 




234 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

are the Portland, Stratton’s Independence, Gold Coin, Hull City Placer (Independ¬ 
ence Consolidated), Isabella, Mary McKinney, Moon-Anchor, and perhaps the 
Victor. To this list should probably be added the C. O. D. mine. Even these 
records do not accurately fix the original water surface, for the Blue Bell tunnel, 
as will be seen, began to drain the district at a very early stage in mining develop¬ 
ment. The mine records show, however, that a former water surface, probably 
not very different from the original water surface, stood from 9,489 to 9,723 feet 
above sea level. As might be expected from the fact that the general slope and 
drainage of the region are westward, the higher water levels were found in the 
eastern part of the district, where the Hull City Placer reached water at 9,723 
feet, the Victor at 9,613 feet (reported), and the Isabella at 9,550 feet, indicating 
a water surface at an average elevation of approximately 9,600 feet. In the 
southern and western parts of the district the Gold Coin reached water at a level 
of 9,396 feet, the Portland at 9,452 feet, Stratton’s Independence at 9,569 feet, the 
Moon-Anchor at 9,489 feet, and the Mary McKinney at 9,498 feet. As the Gold 
Coin mine is entirely in the granite it may be omitted from the present comparison. 
The records of the other mines indicate the former presence of a water surface 
about 9,500 feet above sea. So far as they go, those elevations of “first water” 
that can be accepted as defining approximately the original water surface indicate 
that in the area since extensively opened by underground workings this surface 
sloped westward at a lower angle than the general inclination of the country. If 
the underground water surface had been reached by several shafts before the 
initiation of tunnel drainage, its angle of slope would probably have been found 
even lower. It may be noted in this connection that the 9,500-foot contour (PI. I, 
in pocket), which corresponds to the average elevation of the ground-water surface 
in the southwestern part of the developed area, extends from Wilson Creek, south 
of Victor, around the southwest base of Squaw Mountain to the Economic mill, 
thence to Arequa, thence around Beacon Hill just above the El Paso mine, thence 
to Anaconda, and thence to the’ southeast corner of the town of Cripple Creek. 
This sinuous line lies in general outside of the main contact between the breccia 
and the old granites, gneiss, and schist. It enters the central breccia area, however, 
at Arequa and Anaconda. 

The depth at which water was reached varies from 910 feet in the Isabella to 
35 feet in the Mary McKinney, the latter mine being only a little over 33 feet above 
the 9,500-foot contour at Anaconda. 

As the shafts were deepened, the ground water interfered seriously with mining 
development, and several mines began pumping about the year 1895. It was 
soon found that the cost of lowering the water in this way was a serious burden 
and that it fell chiefly upon a few of the deeper and wetter mines. Such individual 
pumping also revealed certain peculiarities of the ground water which will be 
referred to later. Attention was accordingly turned to tunnel drainage. 


. UNDERGROUND WATER. 


235 


TUNNEL DRAINAGE. 

Although not driven for drainage purposes, the Blue Bell tunnel, near Ana¬ 
conda, is of interest as being the first of the Cripple Creek workings to encounter 
water. This tunnel, which enters in granite at an elevation of 9,335 feet, or about 
15 feet below what seems to have been the average elevation of the original water 
surface in this part of the district, had a maximum flow of 200 gallons a minute. 
Water was issuing from this tunnel in 1894, when Penrose visited it, and the flow 
persisted for several years. The extent to which the Blue Bell tunnel lowered the 
original ground-water surface in the western part of the district, before water was 
reached a year or two later in shafts, can not be determined. Its effect, however, 
was probably slight. 

The Ophelia tunnel enters the granite at the west base of Gold Hill at an 
elevation of 9,268 feet. In December, 1896, this tunnel was 2,600 feet in length, 
with a discharge estimated at from 2,000 to 2,100 gallons a minute. Practically 
all of this water came from the breccia, which the tunnel entered about this time, 
or from open fissure zones that were evidently connected with the main volcanic 
neck. The tunnel maintained this flow for over a year, becoming dry in 1898, 
when the Standard tunnel began to drain the district. 

The Standard tunnel, begun in January, 1896, has its portal in the granite 
of Gold Run, west of Beacon Hill, at an elevation of 9,027 feet. Its objective 
point was not the main volcanic neck, but the phonolite plug of Beacon Hill. In 
February, 1896, the tunnel cut the El Paso vein, whence issued a flow of 250 gallons 
a minute. The water became more abundant as the contact between the granite 
and phonolite was approached, and in 1898, when the phonolite was reached, 
the flow amounted to 1,000 gallons a minute. This rapidly increased as the tunnel 
penetrated the phonolite and in 1899 the maximum flow of from 12,000 to 18,000 
gallons a minute was attained. Work was finally abandoned in June, 1899, when 
the tunnel had been driven 2,800 feet. By the end of 1901 the tunnel was dry, 
having lowered the water levels in the Beacon Hill, Gold Hill, and Raven Hill 
mines, and probably also, to a less recognizable extent, those of the mines in the 
eastern part of the district. 

The Newell tunnel enters Grouse Hill from Arequa Gulch, its portal being at 
an elevation of 8,930 feet. It has not reached the Beacon Hill phonolite nor the 
main volcanic neck, and although its face is 119 feet lower than that of the Standard 
tunnel, it has never encountered any important flow of water. 

The El Paso tunnel, the lowest and most recent drainage tunnel in the district, 
has its portal at an elevation of 8,783 feet, on Cripple Creek, just below the mouth 
of Arequa Gulch and a little less than a mile southwest of the El Paso shaft, with 
which it connects. Work was begun on this tunnel in January, 1903, and on 
September 6 of the same year connection was completed with the lowest level of 
the El Paso mine. 


SUBSIDENCE OF WATER IN FEET 


236 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT 


' WEEKS FROM SEPT. 13,1903 
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 



10000 


9000 


800C 


7000 


6000 


5000 


4000 


3000 


2000 


FLOW IN GALLONS PER MINUTE 

Fig. 22._Diagram showing relation between the subsidence of the water in the Elkton mine and the outflow from the El 1 aso tunnel. 
























































































































































































































































































































































UNDERGROUND WATER. 


237 




The weekly flow from the tunnel, as measured with a Lallie current meter by 
Countryman & Jaquith, the mining engineers who planned the tunnel, is as follows: 


Discharge from the El Paso tunnel September 6, 1903, to December 31, 190 4 . 


Week ending— 

Gallons 

per 

minute.a 

Gallons 
per week .b 

September 13, 1903. 

2,084 

19,595,520 

September 20, 1903. 

1,780 

19,408,810 

September 27, 1903. 

1,840 

18,245,810 

October 4, 1903. 

1,808 

18,389,750 

October 11, 1903. 

1,840 

18,421,500 

October IS, 1903. 

1,819 

18,472,710 

October 25, 1903. 

1,925 

18,800,130 

November 1, 1903. 

2,004 

19,803,570 

November 8,1903. 

1,920 

19,784,720 

November 15,1903. 

1,947 

19,495,730 

November 22,1903. 

2,085 

23,351,430 

November 29, 1903. 

4,259 

35,004,110 

December 6,1903. 

4,835 

45,834,970 

December 13, 1903. 

5,130 

50,220,580 

December 20, 1903. 

5,085 

51,479,100 

December 27, 1903. 

5,174 

51,701,430 

January 3, 1904. 

4,452 

48,512,320 

January 10,1904. 

5,252 

48,908,870 

January 17, 1904. 

0,180 

57,051,950 

January 24, 1904. 

0,494 

03.912,340 

January 31,1904. 

0,211 

04,035,520 

February 7,1904. 

0,404 

03,883,100 

February 14, 1904. 

0,383 

04,749,790 

February 21, 1904. 

0,525 

05,059,050 

February 28, 1904. 

0,398 

05,130,250 

March 6, 1904. 

0,350 

04,250,170 

March 13, 1904. 

0,000 

05,577,460 

March 20, 1904. 

0,470 

66,208,360 

March 27,1904. 

0,758 

60,702,790 

April 3, 1904. 

0,855 

08,610,830 

April 10, 1904. 

0,838 

09,014,740 

April 17, 1904. 

0,805 

08,761,120 

April 24, 1904. 

0,843 

68,785,500 

May 1, 1904. 

0,84'8 

08,997,500 

May 8, 1904. 

0,533 

67,435,000 


f— 


Week ending— 

Gallons 

per 

minute.a 

Gallons 
per week.* 

May 15, 1904. 

6,700 

66,094,300 
65,500,320 
63,836,040 
63,735,850 
63,302, 400 
61,992,000 
60,157,440 
60,066,000 
60,000,240 

59.560.400 

58.167.600 
58,091,040 

57.550.800 
50,330,450 

53.827.200 

51.105.600 
50,406,000 
51,004,800 
51,005,150 
49,392,300 

48.988.200 

49.341.600 

48.334.100 
48,730,000 

49.190.400 
48,384,000 

47.779.200 
47,073,000 

47.115.800 

46.670.400 

46.972.800 

47.880.100 

49.291.200 
49,644,150 

May 22, 1904. 

May 29, 1904. 


June 5, 1904. 


June 12, 1904. 


June 19, 1904. 


June 26, 1904. 

July 3, 1904. 

July 10, 1904. 

. 

July 17,1904. 


July 24, 1904. 


July 31, 1904. 


August 7, 1904. 


August 14, 1904. 


August 21, 1904. 


August 28, 1904. 


September 4, 1904. 


September 11, 1904. 


September 18,1904. 


September 25, 1904. 


October 2, 1904. 


October 9,1904. 


October 16,1904. 


October 23, 1904. 


October 30,1904. 


November 6, 1904. 


November 13. 1904__ 


November 20, 1904. 

November 27, 1904. 

December 4. 1904__ 

December 11, 1904. 


December 18, 1904. 


December 25, 1904. 

January 1, 1905. 



a As measured weekly by Countryman & Jaquith with current meter. 

f> As estimated by Countryman & Jaquith from weekly measurements considered in relation to dates at which prin- ■ 
eipal fluctuations occurred. 


Messrs. Countryman & Jaquith" estimate the total discharge of the tunnel 
to January 1, 1905, at approximately 3,550,000,000 gallons, equal to about 
474,695,000 cubic feet, or 10,900 “ acre-feet,” and weighing approximately 14,834,000 
tons. The same engineers estimate the minimum cost of pumping this quantity 
of water, with an average lift of 500 feet, at $600,000, whereas the total cost of the 
El Paso tunnel was $90,000. 

As was the case with the Standard tunnel, the El Paso slowly lowered the water 
in the Mary McKinney and Elkton mines, showing that there is a connection through 


a Personal letter of February 13, 1905. 


13001 — No. 54—06 - 17 


































































































238 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

« 

open fissures between the Beacon Hill phonolite and the main volcanic neck. The 
relation between the flow from the El Paso tunnel and the fall of the water in the 
Elkton mine is shown in the diagram of fig. 22. 

CONDITION'S OF AVATER STORAGE. 

The records of the various drainage tunnels all suggest the same conclusion, 
namely, that the volcanic neck, filled with breccia and eruptive rocks, contains a 
body of water which is prevented from escaping into the streams of the region by the 
relatively impervious character of the older crystalline rocks of the prevolcanic 
plateau. The relation is suggestive of a water-soaked sponge set in a glass cup. 
That these granites, gneisses, and schists are not strictly impervious is shown by the 
evident connection between the Beacon Hill water and that in the main volcanic 
neck. This connection, however, is certainly due to one or more zones of persistent 
Assuring and not merely to passage through slightly jointed rocks. The fact that the 
tunnels are all comparatively dry until they penetrate the volcanic breccia or until 
they cut open fissures extending into the breccia and that they then receive a sudden 
influx of water followed by a lowering of the water level within the breccia shows that 
natural seepage through the prevolcanic rocks does not exceed the rate of supply to 
the central reservoir. The granite and related rocks undoubtedly contain water to a 
depth of over 2,000 feet, but this water must circulate very slowly, as shown by the 
absence of copious springs in the lower parts of the district, in spite of the consider¬ 
able head of water formerly stored at higher levels in the breccia. For all practical 
purposes, therefore, the underground water of the central part of the Cripple Creek 
district is to be regarded, not as an underground sea extending to indefinite distances 
from the Amlcanic center, but rather as an underground lake or pond bounded by the 
steep walls of the old \ T olcanic throat. In this particular pond, however, rock is far 
more abundant than water, and the simile should not be carried too far. 

SOURCE OF THE AVATER. 

The question of the source of this water is of considerable scientific and prac¬ 
tical importance. The statement is sometimes made that the water never rises after 
being lowered by pumping. This, of course, is not strictly true, otherwise such 
mines as the Gold Coin might long ago have stopped their pumps. It may be well 
doubted whether any wet mine has become dry by pumping alone, though after long- 
continued and heavy pumping, such as has been practiced in the Elkton, Stratton’s 
Independence, and Gold Coin mines, the water seldom rises again to its original level. 
The drainage tunnels have been far more potent in effecting a permanent reduction of 
water level. The facts that these tunnels run dry in a few years and that the springs 
of the district liaA r e never been more than insignificant trickles show that the supply 
of water to this underground reservoir must be small—certainly less than 2,000 
gallons a minute, the quantity which was being pumped from the mines before the 
completion of the El Paso tunnel. Assuming, however, the supply of water to the 
underground reservoir to be at the rate of 2,000 gallons a minute and conservatively 
estimating that the volcanic neck or reservoir has a diameter of 2 J miles, a rough cal¬ 
culation shows that this supply will be maintained if a sheet of water approximately 


UNDERGROUND WATER. 


239 


1 foot in thickness sinks into the ground annually. As the annual net supply to the 
reservoir is certainly much less than the 2,000 gallons a minute assumed above'and 
may be only a small fraction of that quantity, there is evidently no need of supposing 
that the water is supplied from below. Samples of water collected at the bottom of 
the C. K. & X. shaft and from the 1,400-foot level of Stratton’s Independence mine 
were examined by Mr. George Steiger and found to contain little but calcium and 
magnesium sulphates. Though the water at both places spurted from fissures in the 
granite, it lias none of the properties of water that has come up from great depth. 
The underground water is invariably cold, that issuing from the El Paso tunnel in 
April, 1904, having a temperature of 14° C., while the temperature of the air was 16° 
C. Thus the behavior, character, and temperature of the underground water all 
indicate a meteoric origin. It is supplied by the ram and snow that fall upon the 
surface of the district. 

EFFECT OF DRAINAGE ON WATER LEVEL. 

When the underground water was first encountered its surface was more nearly 
level than is usual in a region so accidented as that of Cripple Creek. It is hardly 
probable that the coincidence of water level in the western part of the volcanic area, 
with the elevation of the lowest notches in the granitic rim near Arequa and Ana¬ 
conda, was accidental. It may fairly be concluded that, prior to mining operations,, 
any excess of water over that lost by slow seepage through the walls of the volcanic 
funnel made its escape through these notches to Cripple Creek, and thus determined 
the position of the general surface of permanent ground water. The lack of inequali¬ 
ties in the old water surface more pronounced than those indicated by the recorded 
elevations of “first water” suggests further that the volcanic rocks were sufficiently 
permeable to allow the whole water surface in the volcanic neck to very slowly adjust 
itself, under natural conditions, to these outlets. 

When pumping began, however, this adjustment was soon found to be so slow 
that for practical purposes the underground water is to be regarded as occupying a 
number of separate basins. The different effect of the drainage tunnels in various 
parts of the district suggests the same conclusion. It is certain that the water does 
not flow with equal freedom in all directions and through all rocks of the volcanic 
neck. Some of the inequalities of ground-water surface developed by artificial drain- 
age appear in the accompanying table, which is based on a similar table published by 
Mr. V. G. Hills, 0 supplemented by later data. 


a Eng. and Min. Jour., vol. 76, 1903, p. 117. 



240 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


<*> 

5 , 

•r* 

<ft 


«o 

<*> 

£ 


£ 


i *g L ~ -go. « . 

'•g ® > ^ P 

'*5 oj Oj — 
w £* 


U/ © UU ‘ • w 

3 S £* G © O qj 
: 2 fe 3 i 
15 ft 


Discharge. | 

April, 

1904. 

Galls. 

per 

min¬ 

ute. 

I 









g 

• o • 

. 35 

• Tf • 


t • 

, CC CC • i CD • 

• »o CC • • CC • 

fc^CO 

Galls. 

per 

min¬ 

ute. 



* 

° 1 ^ 




8 

1C 

• © 


300 

200 

5 

Maximum 

discharge. 

Gallons per 

minute. 


O' 

»o 


300 

1,300 

s 


800 

22 

900 

3,260 


30 

Unknown. 

500 

10 

2,150 

1,400 

1,890 

Depth to 
water. 

April, 

1904. 

Feet. 



1,190 

848 

1,055 

1,100 


672 

1,011 

_ 

1,163 

1,200 

1,108 


642 (?) 

1,400 

884 

224 

775 

596 

. 

July, 

1903. 

Feet. 



C^- 

O Q 

y. ~ 

CO c 

1,265 

1,100 


1,208 

1,197 

1,118 

1,109 

1,082 

1,244 

642 

1,400 

881 

362 

717 

514 

703 

Depth 

to 

maxi¬ 

mum 

flow. 

Feet. 

1,340 

1,279(?) 
9,030 
1,265 
1,012 

00 

ci 


1,197 

1,201 

1,000 

800 


700 

1,400 

900 

150 

789 

479 

700 

Depth to 
first 
water. 

Feet. 

e~ g 

O o 05 k o c 

^ O t- g LO yt 

CO ^O d g »o 05 

r-4 M 

g 

ft 

1,220 

513 

ifj 

O 00 O 

TT CD 7C 


243 

275 

700 

150 

311 

35 

Unknown. 


cr. 

GO 


O ■** CO 
T CC ^ 
Oi 05 *C 




© 

fe> 




©* 

.© 

?5 

© 


O 

> 

>» 


-*-> 

u 

ci 

| 

M 

c3 

g 


c3 

ft 


©J 


3> 

^ 3 i w 


o 

ft 

c3 

> 

o> 

3 


© ° 
W*05 

<- 




P ° -a g 


w; 


* § £ 

i is 


O.M ■ 
‘■g £ © 

A'S £ 

w 


Wl 


o 

; o o. 


r ~ 

ft d 


O CO 

Cl I - 
O d 


Cl Cl 
CO I'- 
CO O 


~ r. ~ r. ~ ~ r. 05 


Ci o co co co o ci ci 

Cl l'- © CO © CO t'- 

CIOCIOOOCOO 


CD T}1 © 

O. I- — 

CO Cl o 
oo cT oT 

CO © 

C5 N —« 

© ci © 


c- 

C5 N I- CO 

© CO o 

05 05 —< 05 

•/ s 05 s 


GO »0 d d 
00 »0 05 05 


05 05005 05 01 050^05000505 05 00000000 


£ 




. T?< 

0 C • • 

• * d 

• N 

CC 

oc 

LO 

05 

to 

C 5 

to 



• to 





• © 




to 

CO 

■*r 

LO 


• o 

T 

. . o 

TT 

• • o 

• 05 


d 

05 

LO 

00 

to 

05 

© 

© 

• 05 

05 

• • 05 

05 • 

: : 05 

• CO 

CO 

05 

00 

05 

00 

05 

GO 

C 5 

C 5 


p. 

6 

3 

CO 

£ 

o 


a» o» 

ft ft 


ft 

- 6 
ci lo 5 


Cl Cl CO 


o o o o 


ft 

B 

3 

CO 

£ 

o 


£ 
o 

ft ft 
ft ft 


ft 

g 


£ 

o 

ft 

ft 


ft ft 
g g 


£ 

o 

ft 

ft 


£ ft 

S p 

<D ' 

ft 


ft ft 

S 8 2 8 a B 

© © © CC 2 © 

^ ~ - ., CO CO 

o O 05 o w . 

e» e !> !> 

CO 
*0 


ft ft 


£ 

o 

ft 

ft 


c 

a 

o 

z 


o *o 
05 o’ 


Cl ‘O O 

“l z 

o o 


a 

o 

z 


£ 

c 

ft 

ft 

ft 

g 

3 

CO 

> 

o 

ft 

ft 


g 

o 

z 


to 


00 00 00 00 


O CO Q O 
©•*:©© 
05 CO O’ © 

00 CO 05 05 


CO Cl CO oc 

»D CC O Cl 

00 1-H 05 

oo" GO oT oo* oo" 


CO Cl CO 00 i 1 <. 

■*f LO 00 CO Cl o 

^ X H N 05 g 

oo oo' oT oo oo ±4 

a 
ft 


co ci lo oi r- > 

-f J- -O *-0 ro ^ 

GO n* 05 05 O 

GO 00 05 oo" oc" j2 

e e eg 


CO CO Cl N N O) 05 

t- p- ci —i »-h —i 

O'- TJ1 CO 1 CO o o o 

CO ’ 00 oo" 05 05 oT oT 

e e e 


GO CO Cl 
w 05 LO 
05 CO 'T 


w 

g 

o 

z 


a 

05 »C 05 CO 00 k 

1C LO CO Cl 05 g 

to o lo ^ ■'t* 2 

• » . ^ » c 

05 05 05 05 05 id 

■o o g 


io co -cr io oo co 


r- o 


CO LOCO CO O Cl Cl CO Cl 


9 


■W 05 © lO X IQ 05 

w a x 05/0 n 
cup^coocood^ 

ooooooooo 


x ci x 05 ci x -r ci ’f ci lo 

I- ClCOOLOOOGO^CO»-< 
Cl Cl LO d CO r-H t'. O Cl CO CO 


O O O O O 05 o 


COCOOI^CO — 

^ LO X CO CO Cl 

X N !y N LO |>- 

05 Ol" oi" 05 05 05 


T. 

rz 

O cj 


ft 

3 

o 

u 

o 


fc£) 
ce 

w 

S .s 


g 


c ft 


- 

So 

o 

ft 


>> 

o 


o 

z 


o 

— 

g 




O 

ft 



3 



O 

O 

g 

ci 

g 

d 

g 

d 



bfi 


g 

o 

"ci 

CO 

t-H 

ft 

+5 

X 

03 

.2 

ft 

f- 


© 

V. 

c 

+-> 

_ 

O 

U 

O 

ft 

t- 

O 

q 

ft £ 

d c; 

*» g. 

o 

ft 

o 

M 


-4 

j 

o 




a 

ft 

ft 


CO 

co 

CO 

w 

w 


g c 
g o 

3 


ft 

o 

>> 

M 

CC 

s 


bo 

g 

■2 


ft- 


ci O • 

ftS^ 


Pumping level. b Approximately original ground-water surface. c Drained directly by tunnel or connected mine. 





























































































































Behavior of the underground water in some of the 'principal mines of the Cripple Creek district —Continued. 


UNDERGROUND WATER, 


241 


Esti- 
ma ted 
eleva¬ 

tion 

July, 

1903, 

when 

pump- 

I ing 

stop¬ 

ped. 

Feet. 

9,021 




8 

Ci 

Discharge. 

April, 

1904. 

.o- 






July, 

1903. 

Galls. 

per 

min¬ 

ute. \ 

300 






Maximum 

discharge. 

Gallons per 
minute. 

6,805 

550 

8 § g 

Depth to 
water. 

April, 

1904. 

Feet. 

576 






July, 

1903. 

r© 

ft to 



O oa 

S 3 

Depth 

t<> 

maxi¬ 

mum 

flow. 

Fret. 

576 

750 

■*r o co 

JO oo 

Depth to 
first 
water. 

. —' CO 
■£» <N tO 

£ 1 s 
^ Ci 

to oo o 

1- C* © 

CO H tO 


•C 


- 

53 


O 

H 

be 

*3 


‘C 

o 

>% 

'a5 

«3 

£ 

* 

o 

u 

ft 

04 

< 


ft 

3 

CQ 

o 

o 


> 

o 

K 


J8 3 ?, S 

o o 
od ci ci 


o 

cT 


CO 


8 

. ^ Ci o o © 

>■ Ci CO CO 00 TT 


*- o o o o o> 

>» 

ft 00 Ci ci ci ci' oo’ 






8 

g 

3 

o 


~ 

p 

4-> 

>» 

ft 

4-i 

- 

0) 

.h 

*3 

.3 

3 


O 

> 

to 

| 

04 


^ c-ic • 
> - * g £ 
■2§5£c 
Ws s cc 


^ oo 


- 

— 

53 

!E 


> 

0) 

3 


ft 

s 


w » 

£ £ 
O O 


£ 

o 

o 

ft 


Ci 

00 


O O O 


GC 

*< ^ 


CO CO 
£ £ 


ft ft ft 


O • 
■ r? CO *h 
U 0) 

53 c- 
> a 

S'o Z 
W 


ic 0-3 
(* ~ 52 <2 
<B « d 6 

s .© 5 o 

O ft 


O 53 


c3 

£ 


£ 5 


? & 
2 ^ 




<N 


<N 

CO 

© 



-r 


<N 

i- 

co 

CO 

Ci 

I- 

00 

CO 

& 

Ci 

© 

ci 

Ci 

Ci 

Ci 


S i 

o 'C 
co O 
<3 ft 


O 

ft 


be 5? 


be 

5 


o 

O 


£ 

o 

GO 

c3 

ft 

3 

ft 

4-i 

‘5 


/ 


* 































































242 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

In PL XX an attempt is made to show graphically the behavior of the under¬ 
ground water in the principal mines. A large number of facts, many of which have 
been collected by Messrs. Hills and Mudd, might be cited in illustration of the lack of 
sensitive adjustment of water surface over the district at large to changes artificially 
produced at any one point. A few examples only need be here adduced. 

In July, 1903, the water in the Portland mine stood 557 feet above the pump¬ 
ing level of the adjoining Stratton’s Independence, and had been stationary for 
several months. In April, 1904, the Portland water had fallen only 26 feet, not¬ 
withstanding the facts that pumping has been continuous in the neighboring mine 
and that the El Paso tunnel had been draining the district for seven months. In 
August, 1903, the Portland water was falling from 2 to 3 inches a week. The rate 
evidently increased after the completion of the El Paso tunnel, but how much of 
this increase is to be ascribed to the tunnel and how much to the increased pump¬ 
ing necessitated in Stratton’s Independence mine by the development on level 14 
can not be determined. It is probable, however, that the tunnel has aided in 
lowering the Portland water. In April, 1904, the Elkton water was 15 feet lower 
than the Portland water, whereas in July, 1903, it was 17 feet higher. In July, 
1889, according to Mr. Mudd,® the Portland was pumping 1,500 gallons a minute 
from the 800-foot level, while the Elkton, 40 feet deeper, was dry. According to 
Mr. Hills , b the Clyde mine, on the east side of Battle Mountain, pumped water for 
over a year in 1900-1901, from an elevation of 9,573 feet, when the Modoc, Last 
Dollar, and Portland mines, its near neighbors, were dry at lower elevations. The 
Eclipse mine, between the Portland and Elkton, had, on April 19, 1904, a water 
level 491 feet above that of the Portland, 520 feet above that of the Ajax, and 
506 feet above that of the Elkton. This, as Mr. Hills has pointed out, is one of 
the most remarkable cases of difference of water level to be found in the district. 
It is in a way more striking than the greater discordance between the Portland 
and Stratton’s Independence levels, because at this time neither the Eclipse, Port¬ 
land, Ajax, or Elkton were pumping, and there was supposedly sWe opportunity 
for hydrostatic adjustment. 

The history of the underground water in the Elkton mine is particularly inter¬ 
esting from its illustration of the fact that the water circulates mainly through 
open fissures and not through the general mass of the country rock, and from the 
close connection of this mine with the drainage tunnels. The following account of 
the Elkton water is based upon carefully prepared data which were very kindly 
' furnished us by Mr. Sherwood Aldrich, chairman of the executive committee of 
the Elkton company. 

The first water encountered in the Elkton mine was on level 3, 9,423 feet above 
the sea. The flow ranged from 400 to 600 gallons per minute, but after a few 
months the level became dry, owing probably to drainage through the Ophelia 
tunnel. The flow on level 4 was similar to that on level 3, while successively larger 
amounts of water were encountered on levels 5 and 6. These levels also ultimately 
became dry, being probably drained by the Standard tunnel. In 1900 sinking 
was continued and stations cut at levels 7 and 8. Pumps were placed on level 8 
and drifting was begun from both stations. In February, 1901, the south drift on 


a Manuscript report to the Elkton company. 


b Ninth Ann. Rept. Portland Company, 1903, p. 89. 





. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER NO. 54 PL. XX 



<D 

O 

ffl 

*+- 

L 

3 

in 

L 

0 

id 

"to 

L 

d 

+j 

ID 

C 


qj t 
> o 

a) ffi 
oO m' 

i\ 

D * 
0. 2 


ID 

c 

’-ao 

’l 

o 

X 

ID 

*+- 

(D 

E 

‘x 

o 

L 

Q_ 

a_ 

< 


rO O 
o <r> 
<n — 

L *1 
ID Xl 

-M Q_ 
2 * < 
* L L 


(0 +* Q) Q) 

— Ifl 4- 

q L ^ ‘O 

O iZ 5 5 

i : i 


& 


WATER LEVEL AT VARIOUS DATES IN THE PRINCIPAL MINES OF CRIPPLE CREEK. 














































UNDERGROUND WATER. 


243 


level 7 broke into a cavity, already described, from which a large flow of water 
immediately rushed and, pouring down the shaft, drowned the pumps at level 8. 
In a comparatively short time the water rose to a point about 45 feet above level 7. 
Early in July, 1901, these levels were recovered by pumping and by bulkheading 
the south drift on level 7, whence most of the water issued. Drifting was resumed 
on level 8 near the end of 1901, and the water steadily increased until in July, 1902, 
the pumps were raising from 2,500 to 2,800 gallons per minute. Early in August 
the attempt at further development below the water level was temporarily aban¬ 
doned, pumping was stopped, and the water rose to a point 2.5 feet below level 7. 
During the next thirteen months—that is, until the opening of the El Paso drainage 
tunnel—the water fell about a foot per month, the lowering of the water being 
probably due mainly to the pumping in the El Paso mine. September 6, 1903, the 
tunnel was completed to the El Paso mine and the restraining bulkheads blown out. 
September 7 the water in the Elkton stood at the shaft 29.5 feet below the floor 
of level 7, or 9,015.4 feet above sea level. The first rush of accumulated water 
from the tunnel soon subsided to the normal flow. The following table exhibits 
the subsequent relation of the Elkton water level to the tunnel drainage: 


Relation of water level in Elkton mine to drainage through El Paso tunnel, September 13, 1903, to May 15, 1901,\. 


Date. 

Eleva¬ 

tion 

above sea 
level of 
water in 
Elkton 
mine. 

Flow 
from El 
Paso tun¬ 
nel. 

Weekly 
decrease 
in eleva¬ 
tion of 
Elkton 
water. 

Weekly 
varia¬ 
tions in 
tunnel 
flow. 

Date. 

Eleva¬ 

tion 

above sea 
level of 
water in 
Elkton 
mine. 

Flow 
from El 
Paso tun¬ 
nel. 

Weekly 
decrease 
in eleva¬ 
tion of 
Elkton 
water. 

Weekly 
varia¬ 
tions in 
tunnel 
flow. 

September 13,1903 .. 

Feet. 

9,013.5 

Gallons 

per 

minute. 

2,084 

Feet. 

Gallons 

per 

minute. 

January 17, 1904.... 

Feet. 

8,988.3 

Gallons 

per 

minute. 

6,186 

Feet. 

2.4 

Gallons 

per 

minute. 

+934 

September 20,1903 .. 

9,012.4 

1,780 

1.1 

- 

304 

January 24, 1904... 

8,985. 4 

6,494 

2.9 

■ +308 

September 27, 1903 .. 

9,011.6 

1,840 

.8 

+ 

60 

January 31, 1904... 

8,983.2 

6,211 

2.2 

-283 

October 4, 1903. 

9,010.9 

1,808 

. 7 

- 

32 

February 7, 1904... 

8,981.0 

6,464 

2.2 

+253 

October 11, 1903. 

9,010.3 

1,846 

.6 

+ 

38 

February 14, 1904... 

8,978.7 

6,383 

2.3 

- 81 

October 18, 1903. 

9,009.6 

1,819 

.7 

- 

27 

February 21,1904.. 

8,976.8 

6,525 

1.9 

+ 142 

October 25,1903. 

9,008.8 

1,925 

.8 

+ 

106 

February 28, 1904... 

8,974 8 

6,398 

2.0 

-127 

November 1,1903 ... 

9,008.0 

2,004 

.8 

+ 

79 

March 6, 1904. 

8,972.9 

6,350 

1.9 

- 48 

November 8, 1903 ... 

9,007.5 

1,920 

. 5 

- 

84 

March 13, 1904. 

8,971.0 

6,660 

1.9 

+310 

November 15, 1903 .. 

9,006.8 

1,947 

.7 

+ 

27 

March 20, 1904. 

8,969.0 

6,476 

2.0 

-184 

November 22, 1903 .. 

9,005.9 

2,685 

.9 

+ 

738 

March 27, 1904. 

8,907.3 

6,758 

1.7 

+282 

November 29, 1903 .. 

9,003.7 

4,259 

2.2 

+ 1 

574 

April 3, 1904. 

8,964.3 

6,855 

3.0 

+ 97 

December 6, 1903.... 

9,000.4 

4,835 

3.3 

+ 

576 

April 10, 1904. 

8,962.2 

6,838 

2.1 

- 17 

December 13, 1903... 

8,997.9 

5,130 

2.5 

+ 

295 

April 17, 1904. 

8,959.8 

6,805 

2.4 

- 33 

December 20, 1903... 

8,995.8 

5,085 

2.1 

- 

45 

April 24, 1904. 

8,957.8 

6,843 

2.0 

+ 38 

December 27, 1903... 

8,993.7 

5,174 

2.1 

+ 

89 

May 1, 1904. 

8,955.8 

6,848 

2.0 

+ 5 

January 3, 1904. 

8,992.5 

4,452 

1.2 

- 

722 

May 8, 1904. 

8,954 4 

6,533 

1.4 

-315 

January 10,1904.... 

8,990.7 

5,252 

1.8 

+ 

800 

May 15, 1904. 

8,952.9 

6,700 

1.5 

+ 167 


The data in the foregoing table are graphically shown in fig. 22 (p. 236). It 
there appears that a few days after the El Paso tunnel cut into the great watercourse 
that raised the flow from 2,000 to over 5,000 gallons the water in the Elkton began 
to fall with comparative rapidity. The line in the diagram representing this fall 
is nearly straight and strikingly independent of the subsequent fluctuations in the 
flow from the tunnel, indicating that the rate of fall of the Elkton water is practi¬ 
cally limited by the flowage capacity of the natural fissure which afforded the first 














































244 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


great flow in the tunnel. The water later encountered in the tunnel is apparently 
not connected with the Elkton mine by any important open channels. 

The history of the water of the Elkton mine thus well illustrates the fact that 
the portion of the underground water which need be considered in mining opera¬ 
tions is confined to fissures. It also explains the frequent difference in water 
level in neighboring mines. The few springs in the district appear in some cases 
to be unaffected by the unwatering of deep mines in their vicinity, showing that 
they are not necessarily supplied from a general bod}" of underground water. At 
Arequa, for example, is a spring that has not disappeared in spite of the deep work¬ 
ings at Elkton and under Beacon Ilill. 

All of the existing drainage tunnels have tapped the breccia-filled volcanic 
neck from the west or southwest, and it is from the latter quarter that future tun¬ 
nels, in all probability, will be driven. The effect of each tunnel has naturally 
been most quickly and decisively apparent in what may be called the west-side 
group of mines (PI. XX, p. 242). That the Ophelia tunnel, driven far into the 
breccia and through a number of previously known fissure zones, would drain the 
mines of Raven and Gold hills approximately to its level was almost a foregone 
conclusion. But in the case of the Standard tunnel, directed not for the breccia 
but for the phonolite plug of Beacon Hill, no such result could confidently be pre¬ 
dicted. Fortunately the phonolite proved to be connected by open fissures with 
the main volcanic neck, and there can be no question that it lowered the water 
levels of most of the west-side mines. The Eclipse seems to have been the only 
wet mine not clearly affected. The peculiar behavior of the water in this mine, 
which should perhaps be grouped with the Battle Mountain or Victor mines, has 
already been pointed out and is shown diagrammatically in PI. XX (p. 242). The 
Eclipse water seems to occupy an impervious pocket in the breccia, for which no 
geological explanation has been found. The Standard tunnel undoubtedly drained 
the Gold Hill and Povert}" Gulch mines. 

The effect of the Standard tunnel on the mines of the Victor group is not clear. 
It is supposed to have lowered their water surfaces to some extent, but the con¬ 
tinuous pumping of the Stratton's Independence, Gold Coin, and Strong mines 
has probably been the dominant factor in lowering the water in this part of the 
district. At all events, the effect of the tunnel drainage is not clearly distinguish¬ 
able from that of pumping. As may be seen from PI. XX (p. 242), the pumping 
levels of the Gold Coin and Stratton’s Independence mines are far below the flow 
gradient of the tunnel. 

As regards underground water, the east-side group of mines is divisible into 
two subgroups. One of these includes the mines lying on the western and south¬ 
western slopes of Bull Hill, particularly the American Eagle, John A. Logan, Orpha 
May, Blue Bird, and Last Dollar mines. The shafts of these mines are among 
the deepest in the district, the American Eagle shaft being second only to the 
Lillie (see PI. XI, p. 148), though its sump is 806 feet above that of the Stratton's 
Independence shaft. Notwithstanding their depth, these shafts have had little 
trouble with underground water. This is due to the fact that they were not sunk 
to their present depth until this part of Bull Hill had been drained by the mines 
and tunnels to the west. The American Eagle, John A. Logan, and Orpha May 


I 


UNDERGROUND WATER. 245 

shafts have always been dr 3 T . The Blue Bird reached water in March, 1902, at 
an elevation of 9,057 feet, or 30 feet above the portal of the Standard tunnel, which 
had been dry since the preceding year. This water slowly receded, and in August, 

1902, the sump, elevation 9,026 feet, was dry. The Last Dollar first reached water 
at the same elevation as did the Blue Bird. This soon receded. It was again 
reached at 9,010 feet, hut disappeared after a short period of pumping. After 
the completion of the El Paso tunnel sinking was resumed and no water had been 
encountered up to April, 1904. These facts indicate that the mines of the western 
and southwestern slopes of Bull Hill are effectively drained by the El Paso tunnel. 

The mines of the second subgroup lie on the eastern slopes of Bull Hill and on 
Bull Cliff. They include the Isabella, Victor, Vindicator, Lillie, Findley, Hull City 
Placer, Golden Cycle, and a number of other mines of less depth. These mines 
have all had to contend with water, the burden of pumping falling in recent years 
most heavily upon the Vindicator, which in 1903 was draining the Findley, Hull 
City Placer, and probably the Golden Cycle. Whether the Isabella belongs to the 
same drainage basin is doubtful. 

In the early part of the year 1903 the Vindicator kept down its water to the 
lowest level, 9,012 feet above sea, by pumping from 300 to 550 gallons a minute. 
Under these conditions the Findley, with its sump at 9,103 feet, was dr}\ The 
Findley sank another hundred feet, and in June, 1903, there was a little water 
on this bottom level, apparently corresponding in elevation to the pumping level 
of the Vindicator sump at that time. The water in the Hull City Placer then 
stood at 9,052 feet above sea, the pumps discharging 70 gallons a minute. The 
Golden Cycle, with its sump at 9,066 feet above sea, was kept free of water by 
pumping 50 gallons a minute. During the labor strike in the autumn of 1903 the 
pumps were stopped and the water rose at least 200 feet in the Vindicator, Lillie, 
and Findley mines. The rise in the Hull City Placer and Golden Cycle mines 
appears to have been slightly less. The position of the water on April 19, 1904, 
when the Vindicator had resumed pumping and was discharging 180 gallons a 
minute, is shown in PI. XX (p. 242). At the date of writing (February 1, 1905) it is 
reported that the Golden Cycle mine is holding the water at an elevation of 9,066 
feet by pumping 300 gallons a minute and that the Vindicator has stopped pump¬ 
ing, with its water at approximately 9,200 feet. The Golden Cycle is thus dis¬ 
charging nearly the same quantity of water that the Vindicator was raising in July, 

1903, before the opening of the El Paso tunnel. In other words, the burden of 
drainage has been shifted to the Golden Cycle mine, and that burden has not been 
perceptibly lightened, although nearly a year and a half has elapsed since the 
opening of the tunnel. 

The behavior of the water in these five mines shows that they have a common 
water basin, an artificial change in the water level of any one mine being followed 
.in reasonable time by adjustment in the others. The fact that on the cessation of 
pumping in 1903 the water in this basin rose only to a level 500 feet below the 
original water surface indicates a considerable permanent reduction of the water. 
How much of this is due to the pumping of the Victor and west side groups of mines 
and to the drainage tunnels and how much to the persistent pumping of the Vindicator 
and near-by mines can not be determined. The water of the Vindicator stood, in 


246 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE' CREEK DISTRICT. 


April, 1904, 171 feet above the portal of the Standard tunnel. This gives a flow 
gradient, to the mouth of the tunnel, of about 1 to 82, which, in view of the condi¬ 
tions of flowage through the rocks, does not preclude the possibility that the Standard 
tunnel has aided in lowering the water in these mines. On the other hand, during 
the seventeen months ending December 31, 1904, the El Paso tunnel discharged 
3,550,000,000 gallons of water without perceptibly relieving the mines at Altman and 
Independence. We are forced to conclude that from a practical standpoint the 
existing tunnels do not aid the Vindicator, Lillie, Hull City, Findley, and Golden 
Cycle mines. The same statement probably applies to the Isabella mine, which 
may occupy a local water basin having only imperfect flowage connection with 
that of the Vindicator mine. The long idleness of this mine and the relatively 
high level of its sump (PI. XX, p. 242) leave us somewhat in doubt as to the recent 
behavior of its water. The portion of the district probably drained to a practical 
extent by the El Paso tunnel is shown in fig. 23 (p. 250). 

The isolation of the Vindicator water basin from those of the west side and 
Victor groups is apparently not due to the intervention of any continuous zone of 
massive rock, such as a phonolite or basic dike. The fissure systems of the Vindi¬ 
cator, Gold Cycle, and other mines in the vicinity traverse breccia as well as syenite 
and latite-phonolite, and were the breccia generally permeable there is no reason 
why the water should not drain westward. But the experience gained in under¬ 
ground workings, notably in the Elkton mine, shows that unfissured breccia may be 
practically impervious. The fissure systems of the Altman and Independence 
mines have a general northwest-southeast trend. Between these fissures and those 
those of the west and southwest slopes of Bull Hill is a zone of breccia with intrusive 
masses of syenite and latite-phonolite, which contains, so far as known, no important 
cross fissures that might serve as water channels. In the absence of notable east- 
west or northeast-southwest fissures in this zone is probably to be found the chief 
explanation for the failure of existing tunnels to drain the mines near the eastern 
side of the volcanic neck. 

FUTURE DRAINAGE. 

Mr. Hills has shown® that it is practicable to tap the Cripple Creek volcanic neck 
from the southwest by tunnels at various altitudes down to 6,600 feet. Taking the 
Blue Bird shaft as an objective point, he estimates the lengths of some of the possible 
tunnels as follows: 

* 

Estimated length of possible tunnels in Cripple Creek district. 


Elevation 
of portal 
above sea. 

Length of 
tunnel. 

Feet. 

Feet. 

8,600 

16,000 

8,400 

18,400 

8,200 

19,600 

8,000 

21,000 

7,500 

23,900 

7,000 

29,000 

6,000 

36,000 


a Ninth Ann. Rept. Portland Gold Mining Company, 1903. 










UNDERGROUND WATER. 


247 


A tunnel at 6,600 feet elevation would enter the breccia about 2,000 feet below 
the portal of the El Paso tunnel, would be approximately 7 miles long, and is 
regarded from the engineer’s standpoint as the lowest tunnel practicable. At the 
present stage of mining development in the district, however, it seems inadvisable 
to seriously consider any proposed tunnels below an elevation of 7,500 feet. A 
tunnel at that elevation would be about 4^ miles long and would have its face 
about 1,200 feet below the portal of the El Paso tunnel. Its cost in round figures 
would probably be from $400,000 to $500,000. Whether such a tunnel will be justified 
depends primarily upon the outlook for extensive ore bodies below the El Paso 
tunnel. Even if this outlook should prove encouraging, the wisdom of tunneling at 
an elevation of 7,500 feet rather than at 8,000 feet or higher might well be doubted. 
The justification for deep tunneling depends further upon the question whether 
water is as abundant at greater depth as it is above the El Paso tunnel and whether 
it can pass with sufficient freedom through the rocks to insure effective drainage of 
the major part of the district. 

Knowledge of the number of gallons of water corresponding to a fall of 1 foot 
in the general reservoir would be of great use in planning future drainage operations. 
This problem, however, presents two serious difficulties—(1) the data regarding 
the quantities of water pumped and drained from the district since operations 
began are very incomplete, and (2) it is impossible to determine with accuracy the 
average level of the water at any one time. Mr. S. W. Mudd, in connection,with 
his report to the Elkton Company, collected all the available data and calculated 
that from January 1, 1896, to December 31, 1901, the total quantity of water dis¬ 
charged from the mines and tunnels amounted to 20,005,405,000 gallons. He esti¬ 
mated the general lowering of the water within the same period to be 300 feet, 
giving an average discharge of 66,684,683 gallons for each foot of subsidence. The 
semiannual relations of subsidence and discharge and the pumping data from 
which they are derived are shown in the following table taken from Mr. Mudd’s 
report: 


Quantity of water pumped from the Cripple Creek mines from January 1, 1896, to July 1, 1902. 

[Compiled by Seeley W. Mudd lor a report to the Elkton Company.] 


Period. 


Jan. 

July 

Jan. 

July 

Jan. 

July 

Jan. 

July 

Jan. 

July 

Jan. 

July 

Jan. 


1, 1896,to 

1.1896, to 

1.1897, to 
1, 1897, to 
1, 1898, to 
1, 1898, to 
1, 1899, to 
1, 1899,to 
1, 1900,to 
1, 1900,to 
1, 1901, to 
1, 1901, to 
1, 1902, to 


July 1,1896. 
Jan. 1, 1897. 
July 1, 1897. 
Jan. 1, 1898. 
July 1, 1898. 
Jan. 1,1899. 
July 1,1899. 
Jan. 1,1900. 
July 1, 1900. 
Jan. 1, 1901. 
July 1, 1901. 
Jan. 1,1902. 
July 1,1902. 


Elkton. 


Gallons. 


43,200,000 
105,753,600 
180,403,200 

33.868.800 

97.436.800 
79,120,000 

114.356.800 

123.624.800 

173.836.800 

277.516.800 
302,054,400 

503.884.800 


2,035,056,800 


Mary. 

McKinney. 


Gallons. 


8,304,400 

108.172.800 

158.284.800 

140.313.600 
48,729,600 

174,528,000 

6,912,000 

232.257.600 
360,115,200 

94,003,200 

67,046,400 


1,398,667,600 


Portland. 


Gallons. 


Standard. 

tunnel. 


Gallons. 


52.876.200 

83.635.200 
103,680,000 
156,556,800 
274,742,000 
357,686,000 
145,152,000 

67,046,400 

129,600,000 

71.539.200 
77,414,400 

150,681,600 


1,670,609,800 


115,960,000 
485,568,000 
3,810,240,000 
3,246,912,000 
2,547,072,000 
2,004,480,000 
1,137,024,000 
107,136,000 


13,454,392,000 


Morning 

Glory. 


Gallons. 


45,964,800 
328,220,000 
262,656,000 


636,840,800 


Total 

















































248 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


Quantity of water 'pumped from the Cripple Creek mines from January 1,1S93, to July 1,1902 —Continued. 


Period. 

Moon-Anchor. 

Total. 

Elevation of 
water level. 

Drop in 
water level. 

Amount 
pumped per 
foot of drop 
in water level. 


Gallons. 

Gallons. 

Feet. 

Feet. 

Gallons. 

Jan. 1, 1896, to July 1, 1896 

13,132,800 

13,132,800 




July 1, 1896, to Jan. 1, 1897.. 

40.780,800 

136,857,000 




Jan. 1, 1897, to July 1, 1897.. 

181,735,600 

379,428,800 




July 1, 1897, to Jan. 1, 1898.. 

392,256,000 

9.335 



Jan. 1,1898, to July 1. 1898. 

52,876,800 

517,547,200 

9,305 

30 

17,251,573 

July 1,1898, to Jan. 1.1899. 

236,192,000 

1,234,252,400 

9,285 

20 

61,712,620 

Jan. 1, 1899, to July 1,1899. 

285,120,000 

4,580,895.600 

9,242J 

42$ 

107,785,779 

July 1.1899, to Jan. 1, 1900. 


3,680,948,800 

9,172J 

70 

52,584,983 

Jan. 1. 1900. to Jnlv 1. 1900_ 


2,744,655,200 

9.137J 

35 

78,418,720 

Jnlv 1. 1900. to Jan. 1. 1901__ 

2,540,174,400 

9,102J 

35 

72,576,411 

Jan. 1,1901, to July 1,1901. 


1,892,160,000 

9.082J 

20 

94,608,000 

July 1, 1901, to Jan. 1, 1902. 


908,828,000 

9,057 

25J 

35,640,313 

Jan. 1, 1902, to July 1, 1902. 


984,268,800 

9,035 

22 

44,739,491 

Total. 

809,838,000 

20,005,405,000 


300 

a 66,684,683 





a Average. 


Mr. Mudd was compelled by lack of data to disregard the considerable flow from 
the Ophelia tunnel. He also omits from his calculations the probably small quan¬ 
tity of water that sinks into the ground each year and the water pumped from the 
Gold Coin and Stratton’s Independence mines, probably because he considered these 
mines as outside of the area affected by the drainage tunnels. His general conclu¬ 
sion was that the quantity of stored water decreases as greater depth is attained. 

Recently Mr. A. C. Jaquith® has estimated that during the four weeks ending 
April 10, 1904, the average discharge necessary to lower the water in the Elkton 
mine 1 foot was 34,839,775 gallons. This, taken in connection with Mr. Mudd’s 
figures, indicates that there is less water in the lower part of the subterranean reser¬ 
voir than above. It is certain, however, that the water in the Elkton and Mary 
McKinney mines is lowered more rapidly by the tunnels than in other mines less 
favorably situated, so that a fall of 1 foot in the Elkton does not mean that the 
entire surface of the reservoir has subsided to the same extent. These estimates, in 
short, are at best very rough approximations to the truth. 

The volumetric ratio of the water-bearing spaces to the rock mass as a whole 
can not be determined from existing data. It has been shown that in the spring of 
1904 a discharge of approximately 35,000,000 gallons corresponded to a fall of 1 foot 
in the Elkton and Mary McKinney mines. If the entire volcanic neck were affected, 
if the volcanic rocks everywhere permitted the free passage of water, and if the 
inclosing granite, gneiss, and schist were quite impervious, it would be a compara¬ 
tively simple matter to estimate the approximate area of any given horizontal 
section of the neck and then to calculate the percentage of water-bearing spaces. 
These conditions, however, do not obtain. The rocks are practically impermeable 
except where fissured, and the eastern part of the volcanic neck is but slowly affected 
by the drainage of the western part. The rock mass drained by lowering the water 


“ Oral communication. 









































UNDERGROUND WATER. 


249 


1 foot near Beacon Hill may be compared to part of an exceedingly irregular hori¬ 
zontal lens 1 foot thick near Beacon Hill and thinning to an edge in the northern and 
central parts of the productive area. Within such a mass, however, would be 
pockets of water undrained because not connected by fissures with the artificial 
channel of discharge. Furthermore, certain persistent fissures would probably 
contribute water from points outside of the recognized limit of general drainage. 
It is thus impossible to determine with any approach to accuracy what area a plate 
of rock 1 foot thick and possessing the same water-bearing capacity as the Cripple 
Creek rocks should have in order to contain the quantity of water removed from the 
district when the water in the Elkton is lowered 1 foot. It may be assumed that the 
area of such a plate is equal to that part of the volcanic neck lying south of Globe 
Hill and west of Bull Hill, plus a projecting area to include the phonolite plug of 
Beacon Hill. (See fig. 23.) In such case the volume of rock drained is approxi¬ 
mately 80,000,000 cubic feet. If the water discharged for each foot of subsidence 
is taken at 35,000,000 gallons, the drained water-bearing cavities in the rock con¬ 
stitute about 6 per cent of the whole. If Mr. Mudd’s estimate of approximately 
66,700,000 gallons be accepted as the average discharge per foot of drop above the 
level of the Standard tunnel, then the water-bearing cavities, on the same assump¬ 
tion as before with regard to the area drained, constitute about 13 per cent of the 
rock volume. These rough estimates, it should be observed, relate merely to spaces 
of visible size, due chiefly to fracture, but probably in some cases, as in the Elkton 
mine, enlarged by solution. If the assumption as to area drained is anywhere near 
the truth, even the lower figure of 6 per cent indicates that the aggregate water 
capacity of the fissured rock of the volcanic neck is unusually large for texturally 
nonporous rocks. Similar or more accurate estimates for other regions are lacking, 
so that no close comparisons are possible. The original pore space in coarse assorted 
gravel probably ranges, according to Van IIise, a from 32 to 40 per cent. The water¬ 
bearing spaces in some of the shattered rock in the Moose, Midget, Moon-Anchor, 
and Conundrum mines are probably nearly as porous as coarse gravel, and the large 
water capacity or such portions of the volcanic neck considered in connection with 
the remarkably abundant fissures suggests that the assumed area of the hypothet¬ 
ical plate 1 foot in thickness is not excessive. 

It is probable that at a depth of 1,000 to 1,500 feet below the El Paso tunnel 
open fissures and shattered zones in the breccia will still be sufficiently abundant to 
contain in the aggregate a large body of water, though the amount is likely to be 
smaller than that at the El Paso level. It is probable, also, that the greater part of 
this water can be drawn off by a tunnel, provided that the main tunnel or crosscuts 
are run through fissure zones known to carry abundant water at higher levels. 6 
From a tunnel driven to a point under the Blue Bird shaft it would not be difficult to 
crosscut into the water basin of the Vindicator and Golden Cycle mines. The valu¬ 
able bearing on this problem of the careful record that has been kept of the El Paso 
water can hardly be overestimated. 

a A treatise on metamorphism: Mon. U. S. Geol. Survey, vol. 47, 1904, p. 127. 

6 Press dispatches from Cripple Creek, dated March 27, 1900, bring news that the El Paso mine, which has been opened to 
the 1,000-foot level, or 400 feet below the drainage tunnel, has been flooded. On breaking through the El Paso phonolite dike 
(see fig. 39, p. 3-50) the miners encountered an unexpected flow of water, estimated at from 5,000 to 7,000 gallons per minute, 
which drowned the pumps and in six hours filled the mine to the GOO-foot level. This event shows that the Assuring along the 
C. K. & N. vein constitutes an open and.effective waterway to a depth of at least 400 feet below the present drainage tunnel. 








250 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


Since the completion of the geological work in the district the El Paso, Elkton, 
and other mines have stoped down to the water level established by the El Paso 
tunnel. A new tunnel is now under consideration and a report on the subject of 



Fig. 23.—Diagram showing probable extent of area practically affected by drainage tunnels into Beacon Hill. 


deeper drainage has been prepared by Mr. D. W. Brunton® for the Cripple Creek 
Mine Owners’ Association. He shows that the three most feasible sites for the portal 
of the proposed tunnel are Cape Horn, Gatch Park, and Window Rock, all in the 


a Drainage of the Cripple Creek district: Eng. and Min. Jour., vol. 80, 1905, pp. 818-821. 















































































UNDERGROUND WATER. 


251 


canyon of Cripple Creek. The relative advantages of the three sites are compared 
by him in the following table: 


Comparison of three sites for portal of new tunnel. 


Location of portal. 

Eleva¬ 
tion of 
portal. 

Depth 
below 
El Paso 
tunnel. 

Distance 
to El 
Paso 
shaft. 

Distance 
to main 
water 
channel. 

Distance 
from 
portal to 
tunnel 
shaft. 

Depth of 
tunnel 
shaft. 

Time 

required. 

Cost. 

Depth 

gained. 

Cost per 
vertical 
foot of 
depth 
drained. 


Feet. 

Feet. 

Feet. 

Feet. 

Feet. 

Feet. 

Years. 


Feet. 


Cape Horn. 

8,160 

630 

12,840 

13,840 

8,840 

650 

1.97 

$380,000 

605 

$628 

Gatch Park. 

8,020 

770 

14,550 

15,550 

10,570 

880 

2.1 

430,000 

740 

581 

Window Rock. 

7,660 

1,130 

17,200 

18,200 

12,690 

1,140 

2.5 

510,000 

1,090 

468 


Mr. Brunton recommends a tunnel having its portal at Window llock, though 
he states that either of the other sites would give the district adequate drainage for 
many years. Whichever site be chosen, the new tunnel will probably pass under 
Beacon Hill, tapping the open fissures that have proved so useful in the Standard 
and El Paso drainage projects. From Beacon Hill a branch of the tunnel will in all 
probability be driven east until the east side group of mines are effectively drained. 

According to the latest advices (March, 1906), received during the final revision 
of this report, differences of opinion on the part of the mine owners with regard to 
the most desirable course for the tunnel and the equitable assessment of the cost are 
delaying the initiation of the project. 























CHAPTER XIII.—UNDERGROUND GASES AND TEMPERATURE. 


SUBTERRANEAN GASES. 

GENERAL STATEMENT. 

During the earlier years of development in the Cripple Creek district no unusual 
mine gases were observed, but as the shafts were deepened and the workings extended 
several properties began to experience much annoyance and even serious interfer¬ 
ence with the work, often in spite of vigorous measures to insure ventilation. At 
least one mine has been forced to close down, largely on account of this subtle and 
insidious enemy, and several miners have perished by it. The trouble appears to 
increase as depth is gained, though at what rate can not as yet be ascertained. 
Certain localities are almost exempt, while in other mines not far distant the gas 
issues in large quantities. The gas lias proved to be a mixture of nitrogen and 
carbon dioxide, with some oxygen. 

The subject seemed of sufficient importance to warrant a careful investigation. 
Such facts as have been ascertained are set forth in the following paragraphs. 

COMPOSITION OF AIR. 

Normal air should have the composition shown in the following table: 


Composition of normal air. 


• 

Dry 

Volumes. 

air. 

Weight. 

Average 

air 

(volumes). 

Oxygen. 

20.92 

78 “179.04 
. 94 j 

.04 

23.10 

{ 

20.6 

78.5 

.04 

.86 

Nitrogen. 

Argon. 

Carbon dioxide. 

Water.. 





100.00 

100.00 

100.00 


Comparative specific gravity of air and various gases. 


Air. 1.0000 

Oxygen. 1. 1056 

Nitrogen.9713 

Carbon dioxide. 1. 5290 


The amount of water gas naturally varies and may reach 3 per cent by volume. 
In moist climates it would perhaps average 1.3 per cent by volume or 0.84 per cent 
by weight. The air at Cripple Creek is ordinarily dry, and the elevation above sea 
level is without influence on its percentage composition." 


252 


a Erdmann, H., Lehrbuch der anorganischen Chemie, Braunschweig, 1902, p. 223. 


























SUBTERRANEAN GASES. 


253 


A loss of oxygen by oxidation of pyrite or organic matter, for instance, soon 
makes air unfit for respiration. Air having but 15 per cent of oxygen is dangerous 
or even fatal. 0 

The percentage of carbon dioxide given in the table is often exceeded. Accord¬ 
ing to Cl. Winkler, the exhaust air in the Saxon coal mines averages 0.7 per cent 
C0 2 , but with such an amount the air is still respirable. At 1 per cent the presence 
of C0 2 may produce no special discomfort. With 2 to 2.5 per cent C0 2 the candles 
are extinguished, 6 but, as all miners know, the air can then still be breathed without 
much inconvenience. At 5 or 6 per cent the condition is very dangerous, and any 
excess of C0 2 above this amount is soon fatal. 

The per cent of carbon dioxide may be easily determined in the mine by the 
little portable apparatus devised by Lunge, by which the volume of air which will 
neutralize a given amount of lime water is ascertained, the end of the reaction being 
indicated by the discoloration of a solution of phenol-phtlialein. Such an appa¬ 
ratus is in regular use by the mine inspectors in the alluvial mines of Victoria, 
Australia, and one of these was obtained through the kindness of Mr. Wykeham 
Bayley of the government laboratories in Melbourne. It was soon found to be use¬ 
less, however, for in the Cripple Creek mines the excess of nitrogen may be as dan¬ 
gerous as that of carbon dioxide. Unfortunately no methods for the direct deter¬ 
mination of oxygen are suitable for a compact portable apparatus, and thus physio¬ 
logical effects, together with candles and lamps, afford the only easy and safe method 
of ascertaining the deficiency in oxygen. It was found that the small portable 
acetylene lamp now in common use among mine superintendents and engineers 
offers a fairly safe indication. This lamp will burn long after the candles are extin¬ 
guished, but when it refuses to burn the air is very dangerous. This probably 
indicates about 15 per cent of oxygen. 

Neither nitrogen nor carbon dioxide is directly poisonous, and the effect is in 
both cases due to suffocation. But there is reason to believe that the heavy carbon 
dioxide produces the worse effect by interfering more actively with the diffusion of 
gases in the lungs. It is difficult to say just what deficiency in oxygen may be per¬ 
missible in spaces where men are working continuously. It assuredly should not 
exceed 1 per cent. The air may, of course, be entirely unfit for long-continued use 
while candles are still burning. In general the workings of the Cripple Creek mines 
are well ventilated and contain a very small percentage of carbon dioxide. 

DISTRIBUTION AND MODE OF OCCURRENCE. 

The gas appears chiefly in the western part of the district, where few of the deep 
mines are entirely free from it. It rarely occurs in the eastern part, including the 
mines of Victor and Battle Mountain and the Vindicator and Isabella vein systems, 
although these mines are among the deepest in the district. A little gas may occur 
sporadically in long crosscuts, or small pockets of it may be struck (as in the Hull 
City mine), but as a whole this vicinity is remarkably exempt from it. In this con¬ 
nection it is worthy of note that the veins mentioned form a separate drainage sys- 

a Kohler, O., Lehrbuch der Bergbaukunde, Leipzig, 1900, p. 674. 

b Smith, A. M.. Report on the foul air in the Allendale mines: Special Rept., Dept, of Mines, Melbourne, 1892. 

13001— No. 54—06-18 







254 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

tem which does not freely communicate with the more open rocks and fissures of the 
western half of the district, as is shown by the failure of the drainage tunnels to 
rapidly unwater them. 

In the western part of the district, extending as far east as Eclipse Gulch and 
Bull Hill, gas began to be encountered as depth was attained. In the Wild Horse 
mine it was found at a depth of 1,200 feet, in others at from 500 to 800 feet below 
the surface. It may issue uniformly from the country rock, chiefly from a porous 
and fractured breccia, as in the Ophelia tunnel, or directly from partly open vein 
fissures, as in the Elkton. In many cases, as at the Moose and Conundrum mines, 
it pours out along basic dikes in more or less shattered rocks. Again it may locally 
issue from fractured granite near the contact with the igneous rocks, as in the El 
Paso mine. In places, at periods of low barometer, it will break out and possibly 
entirely fill a mine which at other times is free from it. It may issue almost con¬ 
tinuously from a certain place in a drift, even with good ventilation, producing a 
local barrier of bad air. 

PHYSICAL CHARACTERISTICS AND COMPOSITION. 

The gas is colorless and without noticeable taste or odor. It is stated, how¬ 
ever, that it sometimes, when very strong, appears as a bluish haze If this is cor¬ 
rect, it is no doubt due to its being saturated with water gas, as is the usual case with 
the carbon dioxide of the Victorian deep alluvial mines. It is a heavy gas, normally 
filling the lower part of winzes and drifts up to a horizontal plane defined by the 
sudden extinction of the candles. Apparently, however, its weight is not an unfailing 
characteristic, for it is reported from some places—the Last Dollar mine, for 
instance—as accumulating in the roof of the crosscuts. When the breast of the 
Ophelia tunnel was examined (p. 269) the acetylene lamps barely burned, but no 
difference whatever was noticeable in the amount present on the floor and in the 
back of the tunnel, which is 8 feet high. The percentage of carbon dioxide measured 
was only 0.68. The temperature of the gas is without doubt higher than the normal 
temperature of the mines. This is well shown by the fact that in the nonventilated 
breast of the Ophelia tunnel the temperature is + 58° F. when gas issues, and only 
+ 54 F. on days when gas is absent. In the Conundrum mine the temperature on 
the 600-foot level was + 62° F. when the drift was filled with gas, and only -f- 53° F. 
when, with a higher barometer, the gas had subsided to a point where it filled only 
the winzes. As shown on page 270, the normal increment of temperature in the dis¬ 
trict as measured in gas-free mines is 1° F. in 60 feet. This corresponds to the lower 
temperatures given above, while the higher figures would give an abnormally rapid 
increment. 

Where no determination of moisture is required, the gas can be collected in a 
large bottle, say an acid bottle holding about 2 or 3 liters, simply by filling it with 
water and emptying it in the locality to be sampled. The two samples from the 
Conundrum mine were collected in tins manner. A more accurate apparatus was 
used in the Elkton mine, where the gas issued from a fissure in the roof of the drift. 
It consisted of two 2-liter bottles, stoppered and connected by a rubber tube pro¬ 
vided with pinchcocks. A long rubber tube reached up from the dry gas bottle 
to the fissure and was inserted in it as far as possible. The other bottle was filled 


SUBTERRANEAN GASES. 


255 


with water and its repeated filling and emptying by siphon insured a corresponding 
quantity of dry and pure gas in the dry bottle. 

The two samples from the Conundrum mine, collected under the conditions 
explained on page 262, were analyzed by the department of chemistry of Cornell 
University through the kindness of Prof. L. M. Dennis, the analyst being Mr. L. F. 
Hawley. 

Volumetric analysis of gas from Conundrum mine. 


• 

1 . 

2. 

Carbon dioxide. 

10.2 

8.3 

Oxygen... 

5.7 

10.2 

Nitrogen (by difference). 

84.1 

81.5 



100.0 

100.0 


No methane or other hydrocarbons were found, nor was there any carbon 
monoxide or hydrogen. 

One sample from the Elkton mine, level 7, south, collected by Mr. L. C. Graton 
on April 15, 1904, under conditions explained above, was also forwarded to Professor 
Dennis, who reports on it as follows: 

The gas was received in a 2-liter glass-stoppered bottle, stopper tied in and protected with paraffin-coated 
canvas. 

The analysis was made by Dr. Arthur W. Browne, of the department of chemistry, Cornell University. 
All determinations of absorbable constituents were made over mercury in a Hempel burette provided with a 
water jacket . The absorbents were contained in mercury pipettes that were charged with not more than from 
15 to 25 cc. of the absorbent. In the absorption analysis the first series of results was rejected to avoid errors 
due to incomplete saturation of the reagents with the nonabsorbable constituents. The percentage of water 
vapor was determined in two fresh samples of the gas by absorption with concentrated sulphuric acid, the acid 
being of course saturated with the other constituents of the gas. Nitrogen was determined by sparking the 
unabsorbed residue with an excess of oxygen over a solution of potassium hydroxide. This was first carried 
on in a Winkler-Dennis combustion pipette fitted with an adjustable spark-gap in place of the spiral coil. 
The final experiments, looking to the removal of nitrogen, were made in a Hempel explosion pipette with the 
spark gap slightly widened. When the residue was sparked in this manner with oxygen, contraction took 
place and continued for about forty hours. The mixture was sparkled for several hours after contraction had 
ceased. The spectrum was then observed and nitrogen lines were found to be absent. The excess of oxygen 
was then removed and the inert residue was measured. Spectroscopic examination of this residue revealed 
the presence of argon only. This result was confirmed by comparison (by superposition) with the spectrum of 
an argon tube. The results of the analysis are as follows: 


Volumetric analysis of gas from the Elkton mine. 


Water vapor. 1-4 

Hydrocarbon vapors. 0. 0 

Carbon dioxide. 14. 7 

Heavy hydrocarbons. 0. 0 

Oxygen. 5. 6 

Carbon monoxide. 0. 0 


Hydrogen. 0. 0 

Methane, etc.. 0. 0 

Nitrogen. 76. 8 

Argon. 1.5 


100.0 

I 


This gas may be considered as a mixture of about 25 per cent air, 59 per cent 
nitrogen and argon, 15 per cent carbon dioxide, and 1 per cent water vapor. There 
is considerably more argon present than in normal air. If the air be regarded as an 
accidental admixture the pure gas would consist of about 20 per cent carbon dioxide 
and 80 per cent nitrogen and argon. 






























256 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

PHYSIOLOGICAL EFFECTS. 

The gas produces the usual effects of suffocation. When present in small 
quantities a feeling of oppression and heaviness, with headache, is noted. In larger 
amounts the breathing and the pulse become rapid. If no fresh air is obtained 
collapse follows, often very suddenly and before the full extent of the danger is 
realized. The deaths due to gas have generally occurred in this way and not because 
the escape had been cut off. Nausea, vomiting, and pains in the back are common 
after-effects of a short visit to a gas-filled drift or winze. In some cases men have 
worked one or two days by electric light in places where candles woidd not burn; 
but in such cases utter exhaustion and possibly permanent injury followed. 

CONDITIONS OF OCCURRENCE. 

The miners soon ascertained that in the places affected the bad air was present 
and absent at intervals. The reason commonly assigned was the change of direction 
of the wind, high southwesterly winds being generally supposed to bring out the gas. 
In no mine were barometric observations carried on. While a local influence of 
winds on conditions of ventilation can not be denied, the relations of mine gases to 
barometric fluctuations, as established by investigations elsewhere, suggested an 
inquiry along these lines. A few observations in the Ophelia tunnel and in the 
Conundrum mine soon confirmed the hypothesis that the influx of gas takes place 
during low barometer and that the air is good during periods of high pressure. A 
series of observations extending over eight months was kindly and most efficiently 
carried out for us by Mr. B. F. Tipton, of the Conundrum mine, as recorded on 
page 264. In conjunction with our own data these records prove fairly well that the 
gases are subject to Kohler’s laws, primarily formulated for coal mines, which may 
be expressed as follows:® 

1. The influx of gas increases with falling barometer and decreases with rising 
barometer. 

2. The rapidity of the influx of gas is, roughly, proportional to the rate of 
decrease of pressure, and, conversely, the more rapidly the pressure increases the 
more rapidly the gas disappears. 

3. If a sudden fall of the barometer is followed by a longer period of low pressure 
the gas decreases slowly. If a sudden rise of the barometer is followed by a less 
rapid increase, or if the pressure remains constantly high, the quantity of gas will 
slowly increase. The largest or smallest amount of gas present does not, therefore, 
always correspond to the minimum or maximum of pressure. 

The records kept by Mr. Tipton show that in April and May, as well as in 
November and December, 1904, a great number of sharp fluctuations took place, the 
aneroid varying from 20.1 to 20.7 inches. One or two remarkable exceptions were 
noted. The gas was bad on April 23, with the high stand of 20.6 and a strong 
southwest wind. 

During the summer and fall, from June 9 to October 29, the barometer remained 
steadily at 20.4 to 20.5. During this period slow and curious fluctuations took 
place. From June 9 to August 4 the gas was continuously very troublesome. 


a Kohler, G., Lehrbuch der Bergbaukunde, 5th ed., Leipzig, 1900, p. 682. 











SUBTERRANEAN GASES. 


257 


On August 5, without change in barometer, the gas disappeared, and conditions 
continued good until August 24, the barometer remaining steady. From August 25 
to October 29 the barometer remained at 20.4 to 20.5, and some gas was present at 
intervals. On October 29, for the first time since July 13, the barometer sank to 
20.3 and more gas appeared. On December 15, 23, and 24 the aneroid indicated the 
low pressure of 20 inches, and the whole mine was filled with gas. 

Imperfect as they are, these data seem to indicate that the gas is influenced to 
a lesser degree by some factor besides the atmospheric pressure. If, as seems 
probable, the gases are of volcanic origin and given oil' by a cooling magma, the 
supposition that their pressure is subject to some such fluctuations as appear when 
the barometer is steady, as during the summer months, is not unreasonable. It is 
to be hoped that long-continued and more detailed records, which no doubt will be 
kept in the future at the mines where gas appears, will throw more light upon these 
important questions. 

ORIGIN OF THE GAS. 

Although carbon dioxide may be introduced in mines locally by many natural 
and artificial processes, and although the proportion of nitrogen likewise may be 
increased in places by some such chemical reactions as oxidation of pvrite or com¬ 
bustion of powder, it seems entirely out of the question to account for the mine 
gases at Cripple Creek by such explanations. There is very little timbering used 
from which carbon dioxide could form by decay; there is only a small proportion 
of carbonates and pyrite present in the ores and rocks compared to that in many 
other mines entirely free from gas. Moreover, the fact that practically no gas was 
encountered in the oxidized zone shows that oxidation can not have anything to 
do with its origin. The sudden influx of large volumes in some mines at periods 
of low barometer clearly shows that vast amounts of this dangerous gas are stored 
in the rocks; and as the evil in general increases with depth, it is evidently accu¬ 
mulated mainly below the present workings in the porous volcanic rocks, a con¬ 
clusion also borne out by the fact that the gas has a higher temperature than the 
normal mine air. 

Considering further that exhalations of gases composed of carbon dioxide, 
oxygen, nitrogen, and sometimes also sulphureted hydrogen always take place 
after volcanic eruptions,® and that they frequently continue for a long time after 
the cessation of the igneous outbursts, we believe that the mine gases of Cripple 
Creek represent the last exhalations of the extinct Cripple Creek volcano. If this 
is true, and the evidence in favor of it seems to be strong, the next question is to 
what extent the gases have a magmatic origin, or whether a part of them, at least, 
can be included air. That the carbon dioxide has the former origin will doubtless 
be admitted. That the mine gases collected contain a considerable amount of 
diffused air obtained during their ascent or in the workings is also probable. The 
question whether some of the nitrogen is of magmatic origin is more difficult to 
answer. If the breccia was formed by explosive action, as seems likely, and then 
consolidated in the large vent of the volcano, it is reasonable to suppose that much 

a Henri Moissan analyzed the gases in one of the fumaroles of Guadeloupe, West Indies, with the following result (Comtes 
Rendus, vol. 138, 1904, pp. 936-938): Sulphureted hydrogen, 2.7 per cent; carbon dioxide, 52.8 per cent; oxygen, 7.5 per cent; 
nitrogen, 36.07 per cent; argon, 0.73 per cent. 



258 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

air might have been included in it and that a gradual absorption of oxygen might 
have taken place. On the other hand, it might be contended that the continued 
exhalations of the volcano would long ago have driven out any included air. If 
this is true, the larger part of the nitrogen must be of magmatic origin. 

REMEDIAL MEASURES. 

In many mines no particular inconvenience is experienced by these gases, 
owing to the fact that they issue in relatively small amounts or to exceptional 
facilities for ventilation. At other places the gas has proved a most difficult 
problem. At the Moose mine strong blowers were used with indifferent effect; 
experiments were made both by exhausting the gas and by forcing in fresh air. 
At times of low barometer all measures fail at this and other mines, as the gas 
pours out in irresistible volumes. The very next day the mine may be free from it. 

Many different remedies have been suggested. Where carbon dioxide is the 
only gas to contend with, chemical means, such as absorption by lime, have been 
proposed, but these may without hesitation be put aside as impracticable. No 
doubt powerful blowers would in many cases dilute the air sufficiently, but the 
expense would be a serious matter for many mines. Exhaust fans would appear 
to be less suitable. In the Conundrum mine and in some mines in Gilpin County 
steam pipes have been introduced in the workings, and the condensing steam is 
said to have given considerable relief at times. The only way in which the steam 
acts is probably by promoting a circulation of the air. A blower should give 
better results. In some cases particularly bad places in the drifts have been 
cemented or lined with sheet metal. This is no doubt an excellent remedy as far 
as it goes. It would seem that the only really effective way of combating the evil 
would be to maintain, in emergencies, by means of powerful blowers and properly 
arranged air curtains, a pressure in the workings which would slightly exceed the 
normal atmospheric pressure. This is called the ‘‘plenum” system of ventilation, 
and has been successfully applied in coal mines and in the alluvial mines of Vic¬ 
toria, the objectionable gas being carbon dioxide in the latter case. At least this 
method could be applied to certain parts of the workings. Considerable expense 
and some difficulties would no doubt be connected with it. In case of failure of 
the blowers it would no doubt also increase the danger of the men working in the 
mine, but in some cases it would seem to be the only possible remedy. 

CARBON DIOXIDE AND NITROGEN IN OTHER MINING DISTRICTS. 

Carbon dioxide (carbonic acid) is known to occur at many places, although 
in metal mines it is somewhat rare. In coal mines it may develop by explosion 
of fire damp or by exudation from coal seams; in metal mines the explosives used 
generate a slight amount; locally it may be due to the action of oxidizing sulphides 
on carbonates. The lead mines of Pontgibaud, France, contained much of this 
gas; also those of Alston Moor and Foxdale, England. Carbon dioxide is fre¬ 
quently present in the Thames district on the Hauraki Peninsula, on the north 
island of New Zealand, and here often interferes with the working, especially during 
periods of low barometer. 0 The Hauraki veins intersect late Tertiary andesite. 


a Park, James, The geology and veins of the Hauraki gold fields: Trans. N. Z. Inst. Min. Eng., vol. 1, 1897, p. 23. 






SUBTERRANEAN GASES. 


259 


Carbon dioxide is often very troublesome <in some of the deep alluvial mines 
at Creswick, just north of Ballarat, Victoria. In these mines the gravels of Ter¬ 
tiary river channels are extracted by means of shafts from 300 to 500 feet deep. 
The gravels are covered by thick basalt floors which have been erupted from many 
points in the district. As a rule these gravels contain only a small amount of 
organic matter. The occurrence of these gases has been carefully examined by 
Prof. A. Mica Smith, of the Ballarat School of Mines, who® finds that they issue most 
abundantly during periods of low barometer, that the gases are warmer than the 
normal air of the mine, and that they are heavily charged with moisture. The 
maximum amount of carbon dioxide found was 4.05 per cent, the highest nitrogen 
81.47 per cent, the minimum of oxygen 14.72 per cent. A typical analysis follows: 

Analysis of gas in mines at Creswiclc, Victoria. 


Carbon dioxide. 3.20 

Oxygen. 14. 72 

Nitrogen. 78. 78 

Water. 3. 30 


100.00 

A similar gas appears to be abundant in a great number of mines in the south¬ 
east section of the main Gilpin County district of gold-silver veins. 6 The deposits 
occur in pre-Cambrian gneiss with dikes and masses of andesitic rocks. The gas, 
which is partly, at least, composed of carbon dioxide, issues suddenly in great 
volumes during periods of low barometer and especially following a sudden decrease 
l the barometric pressure. Several fatal accidents are due to the presence of 
his gas. It is heavy and fills shafts and winzes up to a sharply defined line. 

Mr. J. E. Spurr states 0 that pockets of a gas which evidently consisted of 
carbon dioxide were opened in the Tonopah mines at relatively shallow depths. 
The deposits consist of gold- and silver-bearing fissure veins in andesite rocks. 

A heavy gas, probably chiefly carbon dioxide, is very abundant and trouble¬ 
some in the shafts near Rico, Colo. d 

There are few accounts of the presence of nitrogen gas in mines. Only one 
occurrence is quoted in the general literature; it is at the Strinesdale tunnel near 
Stockport, England/ It consisted of 92 volumes of nitrogen, 8 volumes of oxygen, 
and a trace of carbon dioxide. An important occurrence has lately been described 
by Mr. Harry A. Lee, of Denver/ The locality is Creede, a mining district in 
Colorado containing silver veins in Tertiary volcanic rocks. The Happy Thought 
mine is working on a great fault fissure on which a number of other well-known 
mines are also located. The shaft is 1,400 feet deep and the natural ventilation 
excellent. The gas at times issues in great abundance from the vein; the changes 
appear to accord with barometric variations. Nitrogen being slightly lighter than 

a Smith, A. Mica, Report on the foul air of the Allendale mines: Special Rept. Dept, of Mines, Melbourne 1892, p. 24. 

b Collins, Arthur L., Note on the occurrence of carbonic-acid gas in certain veins of Gilpin County, Colo.: Proc. Colorado 
Soi. Soc., vol. 6, 1897-1900, pp. 120-123. 

c Oral communication. 

d Ransome, F. L., Ore deposits of the Rico Mountains, Colorado: Twenty-second Ann. Rept. U. S. Geol. Survey, pt. 2, 
1901, pp. 304, 305. 

* Foster, C. Le Neve, Ore and Stone Mining, 2d ed., London, 1897, p. 479. 

/ Gases in metalliferous mines: Proc. Colorado Sci. Soc., vol. 7, 1897-1900, pp. 163-192. 











260 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


the air the gas accumulates in raises and in the backs of the drifts. According to 
analysis by Mr. W. F. Edwards the gas contains 96.08 volumes nitrogen (by differ¬ 
ence) and 3.92 volumes oxygen. Xo carbon dioxide is present. 

In the cases of the Colorado and New Zealand mines mentioned it seems most 
probable that the carbon dioxide and the excess of nitrogen are exhalations from 
cooling magmas, as they are believed to be at Cripple Creek. 

DETAILED OBSERVATIONS AT CRIPPLE CREEK MINES. 

Eastern part of the district .—The large mines in the immediate vicinity of Victor, 
including the Portland, Stratton’s Independence, and adjacent properties, also 
the Golden Cycle, Vindicator, Hull City, Findley, Isabella, and Victor mines, are 
all practically free from the exhalations which in other parts of the district often 
cause inconvenience. In the Isabella mine the gas accumulated near the end of 
a long crosscut east on level 11. The same is true of a long crosscut toward the 
east on level 11 of the Findley mine; also, in the Golden Cycle, of a crosscut 900 feet 
long, which, near its breast, enters a particularly loose and open mass of breccia. 
The Hull City mine contained a few indications of gas. With these insignificant 
exceptions, no inconvenience has been caused by subterranean gases in the mines 
mentioned. 

Eclipse mine .—The Eclipse mine, situated immediately east of the Elkton, con¬ 
tains some gas. At the time of examination the shaft was filled with water to a 
point 224 feet below the collar. Above this the shaft was filled with gas, rendering 
the first level inaccessible. 

ETkton mine .—In the Elkton mine serious inconvenience is often experienced 
from gases which issue from fissures following the basic dike which traverses the 
property. At times the northern portion of the mine is almost filled with gas, 
especially in the lower levels. It is sometimes necessary to suspend work on this 
account. Xo gas was known above level 6 and until recently the work was not 
really interrupted by it. In the southern part of the mine, on level 7, gases issued 
in considerable quantities from an open crevice in the vein, which is here contained 
in granite, just outside of the boundary line of the breccia. A candle held up to 
this crevice in the roof of the drift would be immediately extinguished, and at 
times this vicinity is entirely inaccessible. A sample of the dry gas as it issues 
from the crevice was collected according to the method indicated on page 254 and 
an analysis gave the result shown on page 255. 

Moose mine .—A heavy gas is exceedingly troublesome in the Moose mine, 
particularly on the levels below 6, which communicate with the surface only 
through the main shaft. It issues copiously from the fissures in the breccia, par¬ 
ticularly from the shattered breccia on the 1,050-foot level, and it was only by 
lining the north drift of this level with sheet tin for a distance of over 600 feet 
that work in the north end was made possible. Powerful suction blowers were 
used to draw out the gas from the bottom level; but on stormy days, presumably 
at times when the barometric pressure is low, the gas pours into the mine, and the 
miners in several instances narrowly escaped suffocation. It is said that at such 
times, in spite of the adit connection in level 6, the gas has issued from the collar 
of the shaft in such abundance as to at once extinguish a candle. The gas collects 


SUBTERRANEAN GASES. 


261 


in winzes, from which it can be bailed or sucked out when the barometer is high, 
but when the barometer is low the gas enters more rapidly than it can be removed. 
The presence of a moderate amount of the gas in the mine atmosphere is said to 
produce irregular heart action, sweating, and weakness. If these warning symptoms 
are not heeded, asphyxia may suddenly follow. The mine was closed in March, 
1904, partly on account of the difficulty of working in the lowest levels. 

Last Dollar mine .—This mine was not troubled by gas until level 10 was 
developed. On this level, at the breasts of certain long crosscuts, a considerable 
amount accumulates at times. The gas does not interfere with the ordinary 
working of the mine. It is stated that it sometimes accumulates in the back of 
the drifts instead of on the floor; if correct, this would indicate that it is largely 
composed of nitrogen. Miners have worked in the gas for one or two days by 
electric lights when the candles would not burn, but were unable to continue longer, 
as great lassitude and pains in the back developed. 

Modoc mine. —The upper workings do not contain gas, but a 400-foot winze 
in the lower part of the workings always contains some gas and is sometimes 
entirely filled. 

Blue Bird mine. —Gas enters the mine in all levels below 4 on certain days. 
At these times the lower part of the mine is frequently inaccessible. 

Wild Horse mine. —The depth of the Wild Horse mine is 1,250 feet, the elevation 
of the collar being 10,653 feet. Complete oxidation extended down to a depth 
of 1,150 feet. There was no gas until the 1,250-foot level was opened, when it 
issued in large volumes from the porous pyritic granite-breccia which constitutes 
the country rock. The gas interfered greatly with the work and is said to have 
sometimes filled the mine almost to the collar of the shaft for several days in 
succession, especially at periods of low barometer. 

Logan and Orpha May mines. —A few records from these mines, which were 
closed in 1904, were secured from Mr. Fred Johnson, formerly in charge of the 
properties. lie states that gas was very troublesome in a crosscut east on level 
13 in the Orpha May. It also issued in large amounts from a certain place in a 
crosscut on level 12 of the Logan mine, about 500 feet northwest of the shaft. 
Ventilation had no effect, and the place was ordinarily inaccessible, so that the 
drift was temporarily barred. It is stated that the gas had the appearance of a 
“bluish haze” and that it was unusually concentrated and poisonous. Two men 
were suffocated at this place trying to make their way through it. 

Doctor-Jack pot mine. —Gas enters this mine at nearly all points where there 
are open fissures and accumulates wherever the ventilation is defective. Owing 
to the closing of the Doctor shaft, the levels above 10 are'filled with the gas, which 
flows down the shaft to level 10. Here, however, it is carried out by ventilation 
through the stopes and the Advance No. 2 shaft. The 550-foot Morning Glory 
level was so filled with gas beyond the Doctor shaft as to be inaccessible at the 
time of visit. The gas appears to be chiefly carbon dioxide, probably mixed with 
nitrogen. It is said to be particularly troublesome on days when the barometer 
is low. 

The neighboring Mary McKinney mine is practically free from gas. 


262 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

El Paso and C. K. & N. mines .—An abundant flow of gas, in part carbon 
dioxide, issues from some of the fissures of the C. K. & N. lode, at a depth of 300 
feet, so that a candle held to such an opening is immediately extinguished. Owing 
to the connections with the El Paso and Old Glory shafts, the mine was well 
ventilated and the gas was causing no particular inconvenience. 

In the El Paso tunnel, a few hundred feet from the regular El Paso workings, 
gas sometimes issues from granite near the phonolite in such volumes that the 
rapidly flowing stream of water coming from the heading of the tunnel and the 
resulting brisk circulation of air in the drift are insufficient to carry it away. 
At such times candles, torches, and acetylene lamps are extinguished. While no 
actual fissures were found from which the gas issued, the zone from which gas 
comes is narrow and well defined. 

Pointer and Mint mines .—The Mint shaft is 750 feet deep and is sunk in breccia, 
while that of the Pointer is 530 feet deep, latite-phonolite being the country rock. 
Both mines contain much gas, which often seriously interferes with their operation. 
This gas collects in nearlv all crosscuts and drifts not in the direct line of ventilation 
between the two shafts. A considerable part of the workings was found to be 
inaccessible from this cause at the time of visit. 

Poverty Gulch .—Of the mines in this vicinity the Abe Lincoln contains a small 
amount of gas in the winze below the Cripple Creek and Chicago drainage tunnel, 
close to the Half Moon vein. There is also a little gas in the winze below the 
500-foot level. 

In the Mollie Kathleen the air on the 700-foot level is often so bad that candles 
fail to burn, especially when a brisk southwest wind is blowing. 

In the C. O. D. mine, the lower levels of which are not worked at present, 
gas stands several feet deep above the bottom level, 800 feet below the surface. 

Conundrum mine .—Tins mine, which is situated on the eastern slope of Gold 
Hill, contains at times a large amount of gas, which interferes very seriously with 
the working of the property. The deposit consists of a basic dike in a very much 
shattered gneiss, whence the gas escapes in large quantities. The workings con¬ 
sist of an adit 300 feet long with an incline shaft at the end. The lowest (sixth) 
level is 625 feet below the adit, and the workings where most of the gas issues 
are approximately 725 feet below the surface. The workings, as shown in fig. 24, 
partly connect with those of the adjoining Midget mine, which is also much troubled 
by gas. The ventilation is not perfect, the air current entering an old incline near 
the mouth of the adit; thence descending through the workings and winzes to level 
6, from which point it ascends through the incline and leaves the mine through the 
adit. The connection with the Midget mine on level 6 is closed by an air curtain. 
It will be seen that there is practically no difference in level between the intake 
and the upcast current. An attempt is made to increase the ventilation by a sail 
stretched above the winze at the mouth of the adit so as to catch the prevailing 
southerly or southwesterly winds. On days of low barometer gas enters the mine 
from practically all points on level 6, and when the barometer is exceptionally 
low it may fill the whole mine. Work is frequently impossible for many days in 
succession. On March 20, 1904, when the barometer stood at 19.9 inches at the 
portal, the mine was visited. Candles would burn at the shaft station on level 6, 


SUBTERRANEAN GASES. 


263 


but immediately north of the shaft even acetylene lamps were at once extinguished. 
Breathing was very difficult and a feeling of great distress was produced by remain¬ 
ing for only a few minutes in the drift just north of the shaft. It was possible, 
however, to penetrate to a winze 12 feet deep and 100 feet north of the shaft, at 

Midget shaft projected 



Fig. 24.—Longitudinal section showing ventilation in the Conundrum and Midget mines. 

which point a sample of gas was collected by lowering and emptying a bottle filled 
with water. The temperature at this point was +16.7° C. ( + 62° F.). This sam¬ 
ple of gas was analyzed by Mr. L. F. Hawley, of Cornell University, with the fol¬ 
lowing result: 

Analysis of gas from Conundrum mine, March 20, 190If. 


Carbon dioxide. 10. 2 

Oxygen. 5.7 

Nitrogen (by difference). 84.1 


100.0 

On March 21 the mine was again visited. The temperature at the mouth of 
the adit was —2° C. ( + 28° F.), while the barometer stood at 20.2 inches. Work 
was in progress on level 6, but a winze 50 feet deep and 185 feet north of the shaft 
was found to be completely filled with a heavy gas, practically to the level of the 
































































264 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


rail. An acetylene lamp lowered into it was immediately extinguished at a cer¬ 
tain sharply defined line. The temperature at this place was +11.5° C. ( + 53° F.). 
A sample of the gas contained in the winze was collected by the same method as 
before, and as analyzed by Mr. Hawley contained the following proportions: 

Analysis of gas from Conundrum mine, March 21, 190l/.. 


Carbon dioxide. 8. 3 

Oxygen. 10. 2 

Nitrogen (by difference). 81. 5 


100 . 0 


A short distance north of the winze the air in the drift was examined and 
found to contain 0.11 per cent carbon dioxide. Near this point a crosscut several 
hundred feet long extends in a northeast direction into the Moon-Anchor ground. 
This crosscut was found to be full of gas, and could be traversed only to a point 
150 feet northeast of the junction. Here the temperature was +15° C. ( + 59° F.), 
or 6° warmer than at the winze, which was only 200 feet distant. The air at this 
place contained 1.3 per cent dioxide. The acetylene lamps barely burned, and the 
atmosphere was exceedingly oppressive and distressing. 

The conditions described continued during the remainder of the year 1904. 
In addition to the natural circulation indicated above, a steam pipe was carried 
down into the workings, and some benefit is said to have been derived from forc¬ 
ing steam into the drift. During the last days of December a man was suffocated 
on level 6 while attempting to enter this bottom level alone during a time of low 
barometer. His body was recovered in twenty minutes, but it was found impos¬ 
sible to resuscitate him even b} r the immediate use of oxygen. 

Since March, 1904, Mr. B. F. Tipton, superintendent of the Conundrum mine, 
has kept a complete record of barometer readings in order to ascertain the con¬ 
nection between the influx of gas and the atmospheric pressure. This important 
record follows, copied in full. It is to be hoped that at other mines where gas is 
known to exist a barometer will always be kept and records preserved. 

Record of barometric stand and gas conditions in the Conundrum mine, Cripple Creelc, on 600-foot level. 


April 21 
April 22 
April 23 

April 24 
April 25 
April 26 
April 27 
April 28 

April 29 

April 30 
May 1.. 
May 2.. 
May 3.. 
May 4.. 


Date. 


Barome¬ 
ter at 
portal 
of adit. 


1904. 


Air conditions in mine. 


Weather conditions. 


20.3 
20. 4 

20.4 


Very bad; candles will not burn.. 

Good. 

Gas rising; candles will just burn 


20.6 

20.7 

20.5 

20.5 

20.3 


First-class. 

Good. 

A little gas, but lights will burn... 
No gas on levels; winzes are full... 
Gas very bad; lights will not bum 


20.3 

20.7 

20.4 
20.2 
20.3 
20.3 


Gas 2 feet in bottom of levels; lights burn well in 
back of levels. 

First-class. 

Gas rising, but candles will burn. 

Candles will not burn. 

Good. 

_do. 


Sunny; cloudy and snow. 
Sunny. 

Sunny; high southwest 
wind. 

Snow; high wind. 

Sunny; no wind. 

Sunny. 

Do. 

Sunny and high southwest 
wind. 

Cloudy; north wind. 

Snow. 

Cloudy. 

Snow. 

Sunny. 

Do. 









































SUBTERRANEAN GASES 


265 


Record of barometric stand and gas conditions in the Conundrum mine, Cripple Creek, on 600-foot level — 

Continued. 


Date. 

Barome¬ 
ter at 
portal 
of adit. 

Air conditions in mine. 

1904. 



May 5. 

20.4 

Good. 

May 0. 

20.4 

.do. 

May 7. 

20.3 

Bad. 

May 8. 

20.7 

Good. 

May 9. 

'20.5 

.do. 

May 10. 

20.4 

Gas rising. 

May 11. 

20.5 

First-class. 

Mav 12. 

20.4 

Good. 

May 13. 

20.5 

First-class.... 

May 14. 

20.5 

Good. 

May 15. 

20.3 

Gas rising- candles just burn 

May 16. 

20.4 

Good. 

May 17.•_ 

20.5 

Good on levels- gas in winzes and shaft. 

Mav 18. 

20.4 

Bad. 

May 19. 

20.3 

Bad; candles will not burn... 

May 20. 

20.4 

Good. 

May 21. 

20.5 

First-class.. 

May 22. 

20.4 

Good on levels, winzes, and shafts. 

May 23. 

20.6 

Candles will not bum. 

May 24. 

20.2 

Very bad. . 

May 25. 

20.2 

.do. 

May 26. 

20. 4 

Good. 

May 27. 

20.4 

Gas rising, but candles bum. 

May 28. .. 

20.4 

Good. 

May 29. 

20. 4 

.do. 

May 30. 

20.4 

Candles will not burn. 

May 31. 

20.3 

.do. 


20.3 

.do.• 


20.2 

.do. 


20. 1 

.do. 


20.3 

Good. 


20. 4 

.do. 


20. 4 

.do. 


20.5 

.do. 


20. 4 

.do. 


20. 4 

A little gas. 

June 10. 

20.5 

.do. 

June 11. 

20.5 

.do. 

June 12. 

20.5 

.do. 

June 13. 

20.5 

.do. 

June 14. 

20.5 

Candles will not burn. 


20.5 

.. .do. 


20.5 

.do. 


20.5 

Good. 


20.5 

Candles will not burn. 


20. 5 

.do. 


20.5 

.do. 


20.5 

.do. 


20.5 

. .do. 


20.5 

. .do. 


20 5 

. .do.. 


20. 5 

. .do. 


20.5 

_do. 

J une 27. 

20 5 

.do. 


Weather conditions. 


Sunny. 

Do. 

Snow. 

Sunny. 

Do. 

Do. 

Do. 

Do. 

Do. 

Cloudy. 

Do. 

Snow. 

Sunny. 

Cloudy. 

Sunny. 

Do. 

Sunny; snowfall. 

(?) 

Sunny and high southwest 
wind. 

Sunny. 

Cloudy and rain. 

Cloudy. 

I 

Sunny. 

Cloudy. 

Sunny. 

Do. 

Do. 

Do. 

Cloudy. 

Snow. 

Do. 

Cloudy and cold. 

Do. 

Sunny. 

Rain. 

Cloudy and rain. 

Do. 

Do. 

Do. 

Do. 

Sunny. 

Do. 

Rain. 

Cloudy and cold. 

Cloudy and rain. 

Sunny. 

Do. 

Do. 

Do. 

Do. 

Rain. 

Do. 

Hard rain. 

Sunny. 





















































































































































266 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT, 


Record of barometric stand and gas conditions in the Conundrum mine, Cripple CreeTc, on 600-foot lend — 

Continued. 


Date. 

Barome¬ 
ter at 
portal 
of adit. 

Air conditions in mine. 

Weather conditions. 

1904. 

June 28. 

20.5 

Candles will not bum . 

Sunny. 

Do. 

June 29. 

20.5 

.do... 

June 30. 

20.5 

.do. 

Hard rain. 

July 1. 

20.5 

.do. 

Hail and rain. 

July 2... 

20.4 

.do. 

Sunny. 

Rain. 

J uly 3. 

20.5 

.do. 

July 4. 

20. 4 

.do. 

Sunny. 

Clear. 

July 5. 

20.3 

.do. 

July 6. 

20. 4 

.do. 

Foggy and showers. 

Do. 

July 7. 

20. 4 

.do. 

July 8. 

20. 4 

.do. 

Clear. 

July 9. 

20.6 

.do. 

Do. 

July 10. 

20.5 

.do. 

Cloudy. 

Clear. 

July 11. 

20.5 

.do. 

July 12. 

20. 4 

.do.... 

Cloudy and rain. 

Clear. 

July 13. 

20.3 

.do. 

July 14. 

20. 4 

.do. 

Do. 

July 15. 

20. 4 

.do. 

Do. 

July 16. 

20. 4 

.do. 

Do. 

July 17. 

20. 4 

.do. 

Clear and hot. 

July 18. 

20.6 

.do. 

Do. 

July 19. 

20.6 

.do. 

Rain and hail. 

July 20.. 

20.5 

.do. 

Do. 

July 21. 

20.5 

.do. 

Do. 

July 22. . 

20.5 

.do. 

Do. 

July 23. 

20.5 

.do. 

Do. 

July 24. 

20.5 

.do. 

Do. 

July 25. 

20.5 

.do. 

Do. 

July 26. 

20.5 

.do.. 

Do. 

July 27. 

20.5 

Candles will not bum, but gas lower. 

Heavy rain and hail. 
Heavy rain and lightning 
Cloudy; no rain.' 

Rain; sunny. 

Do. 

July 28. 

20. 4 

Candles will not bum below level 5. 

July 29. 

20.3 

Gas rising. 

July 30. 

20. 4 

Gas the same. 

July 31. 

20.4 

Air good on level 4. 

August 1. 

20.5 

Gas lower in the morning. 

Heavy rain. 

August 2. 

20.5 

Gas rising. 

Sunny. 

August 3. 

20.5 

Reached station at level 6. 

Cloudy; clear. 

Do. 

August 4. 

20.4 

Good above level 6... 

August 5... 

20.5 

Air good. 

Rain and hail. 

August 6. 

20.5 

.do. 

Rain; sunny. 

Do. 

August 7. 

20.5 

.do. 

August 8. 

20. 5 

.do. 

Cloudy; sunny. 

Do. 

August 9. 

20.5 

.do. 

August 10... 

20.5 

.do. 

Clear. 

August 11. 

20.5 

.do.... 

Do. 

August 12. 

20.5 

.do. 

Clear; cloudy. 

Do. 

August 13. 

20.5 

.do. 

August 14. 

20.5 

.do. 

Do. 

August 15. 

20.5 

.do. 

Rain and hail. 

August 16. 

20.5 

.do. 

Do. 

August 17. 

20.4 

.do. 

Rain. 


20.4 

.do.... 

Do. 


20. 4 

.do. 

Clear. 

August 20. 

20.4 

.do. 

Do. 












































































































































































SUBTERRANEAN GASES. 267 


Record of barometric stand and gas conditions in the Conundrum mine, Cripple Creek, on 600-foot level — 

Continued. 


Date. 

Barome¬ 
ter at 
portal 
of adit. 

Air conditions in mine. 

Weather conditions. 

1904. 

August 21. 

20. 4 


Rain. 

August 22. 

20.5 

.. .do. 

Clear. 

August 23. 

20.5 

.do. 

Do. 

August 24. 

20.5 

Candles will burn. 

Do. 

August 25. 

20.6 

.. .do. 

Cloudy. 

Rain. 

August 25. 

20.5 

.do. 

August 27. 

20.5 

.. .do.'. 

Clear. 

August 28. 

20.5 

.do. 

Cloudy. 

Rain. 

August 29. 

20.5 

. _.do. 

August 30. 

20.5 

.. .do. 

Do. 

August 31. 

20. 4 

Some gas after noon. 

Clear. 

September 1. 

20. 4 

Candles will burn.. 

Rain. 

September 2. 

20.5 

,. .do. 

Cloudy. 

Clear. 

September 3. 

20.5 

Air good. 

September 4. 

20. 4 


Do. 

September 5. 

20. 4 

. .do. 

Do. 

September 6. 

20.5 


Do. 

September 7. 

20. 4 

.. .do. 

Do. 

September 8. 

20. 4 

Some gas to-day. 

Do. 

September 9. 

20.4 

Mine closed. 

Do. 

September 10. 

20. 4 

Air fairly good. 

Do. 

September 11. 

20.4 

Bad. 

Do. 

September 12. 

20.4 

Air fairly good. 

Do. 

September 13. 

20.5 

.do. 

Do. 

September 14. 

20.5 

. .do. 

Do. 

September 15. 

20.4 


Cloudy. 

Do. 

September 16. 

20.4 

.. .do. 

September 17. 

20.5 


Clear. 

September 18. 

20.5 

.. .do.... 

Do. 

September 19. 

20.5 

. .do. 

Do. 

September 20. 

20. 4 

.. .do. 

Rain. 


20.5 

do . 

Do. 

September 22. 

20. 4 

. .do. 

Cloudy. 

Do. 


20. 4 

.do. 

September 24.... 

20. 4 

.. .do. 

Clear. 


20.5 

.do. 

Do. 

September 26. 

20.5 

.do. 

Do. 

September 27. 

20.4 

.do. 

Cloudy. 

September 28. 

20.5 

.do. 

Do. 

September 29. 

20.4 

.do. 

Clear. 

September 30. 

20.4 

.do. 

Do. 


20. 4 

A little gas- candle will burn. 

Clear and warm. 


20.3 

.. .do. 

Do. 


20.3 

Gas bad after noon. 

Do. 


20.3 

Some gas in winze. 

Do. 


20.3 

.do. 

Do. 


20.3 

.do. 

Do. 


20.3 

.. .do. 

Do. 


20.3 

_do. 

Do. 


20.3 

_do. 

Do. 


20. 3 

. .do. 

Do. 

November 7. 

20.4 

Good air. 

Do. 

November 8. 

20.4 

.do. 

Do. 

November 9. 

20.3 

Ran men out at 2 p. m. 

Snowing. 

November 10. 

20.3 

Candle will not burn; gas very bad. 

Do. 








































































































































































268 


GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT 


Report of barometric stand and gas 


conditions in the Conundrum mine, Cripple Creelc, on 600-foot level — 
Continued. 


Date. 

Barome¬ 
ter at 
portal 
of adit. 

Air conditions in mine. 

Weather conditions. 

1904. 

November 11. 

20.4 

Good. 

Clear. 

November 12. 

20.3 

Good on levels, bad in winzes. 

Do. 

November 13. 

20.3 

.do. 

Do. 

November 14. 

20.3 

.do. 

Clear and warm. 

November 15.... 

20.3 

Very bad. 

Do. 

November 16. 

20. 4 

Good air. 

Do. 

November 17. 

20. 4 

.do. 

Do. 

November 18. 

20.2 

Candle will not burn. 

Warm and high wind. 
Warm. 

November 19. 

20.3 

Candle will just bum. 

November 20. 

20.3 

.. .do. 

Do. 

November 21. 

20. 4 

Good air. 

Clear and warm. 

November 22 . 

20. 4 

Some gas. 

Cloudy. 

Clear and wami. 

November 23. 

20.4 

.do. 

November 24. 

20.3 

Candle will not burn. 

Do. 

November 25. 

20.3 

.do. 

Do. 

November 26. 

20. 4 

Air good. 

Do. 

November 27. 

20.3 

Candle will not burn. 

Do. 

November 28. 

20.2 

Candle will not bum- gas very bad. 

Warm. 

November 29. 

20.3 

Some gas. 

Sunny and cold. 

Do. 

November 30. 

20.3 

...do. 

December 1. 

20.2 

Air bad. 

Sunny and warm. 

Sunny and cold. 

Do. 

December 2. 

20.2 

.do. 

December 3. 

20. 4 

No gas. 

December 4. 

20. 4 

.do. 

Do. 

December 5. 

20.5 

.do. 

Sunn} - and warm. 

Do. 

December 6. 

20.5 

.do. 

December 7. 

20.4 

.do. 

Do. 

December 8.,. 

20.3 

A little gas. 

Do. 

December 9. 

20.2 

Gas on levels and very bad in winzes. 

Do. 

December 10. 

20.2 

Candle will not burn. 

Snow at night. 

Clear and cold. 

December 11. 

20.3 

Good air. 

December 12. 

20.1 

Gas verv bad. 

Cloudy. 

Clear and cold. 

December 13. 

20.2 

No gas. 

December 14. 

20.2 

.do. 

Do. 

December 15. 

20 

Mine full of gas. 

Cloudy and windy. 

Clear and cold. 

December 16. 

20.4 

Air first class. 

December 17. 

20.3 

.do. 

Do. 

December 18... 

20. 4 

.do. 

Do. 

December 19. 

20. 4 

.do. 

Do. 

December 20. 

20. 4 

.do. 

Do. 

December 21. 

20.2 

Gas very bad. 

Clear and warm. 

December 22. 

20.1 

.do. 

Cloudy and cold. 

Snow. 

December 23. 

20 

Mine full of gas. 

December 24. 

20 

.do. 

Sunny. 

Snow. 

December 25. 

(°) 

20 


December 26. 

Gas in mine. 

Cold and snowy. 

Clear and cold. 

December 27. 

20.2 

Air first class. 

December 28. 

20.3 

.do. 

Do. 

December 29. 

20.2 

Good on levels. 

Clear and warm. 

December 30. 

20.2 

Some gas. 

Do. 

December 31. 

20.2 

.do. 

Do. 




o Nobody at mine 














































































































































UNDERGROUND GASES AND TEMPERATURE. 


269 


Ophelia tunnel .—The portal of the Ophelia tunnel is located on the east side of 
Cripple Creek, about half a mile south of the town. The elevation is 9,268 feet. 
The tunnel starting in granite soon penetrates the breccia and continues in this rock 
to the end, the breast being somewhat over 7,000 feet distant and almost due east of 
the portal. Considerable difficulty was experienced with the gas when the tunnel 
was driven, especially in the last 700 feet beyond the surface connections through 
the Mary McKinney and Callie workings. At times work had to be suspended and 
frequently, it is said, gas issued from every new bore hole drilled in the breast. In 
March, 1904, work had been stopped for some time owing to other reasons. During 
a visit on March 5, 1904, the temperature at the portal was —3° C. ( + 26° F.) and 
the barometer stood at 20.5 inches. At the World’s Fair drift, 300 feet south of the 
main tunnel, the temperature was +48° F. Near the caved end of the drift on the 
Howard flat vein, 4,605 feet from the portal, the temperature was 50.5° F. At 
6,610 feet from the portal the temperature was 58° F. and candles burned with diffi¬ 
culty, though the percentage of carbon dioxide was only 0.25, and 2 per cent is 
usually considered necessary to extinguish them. This seemed to point clearly to 
the presence of some other gas besides carbon dioxide. At 6,870 feet from the 
portal the temperature was 58° F., the candles were extinguished, and the percentage 
of carbon dioxide in the air was 0.47. At the breast of the tunnel, about 7,000 feet 
from the portal, acetylene lamps barely burned, the temperature was 58° F., and the 
percentage of carbon dioxide was 0.68. 

At a subsequent visit, on March 18, the temperature at the portal was 45° F., 
and the barometer indicated 20.7 inches. The temperature at the breast was 54° F. 
The air was good, and candles burned brightly up to the breast. 

Copper Mountain .—The only record of gas conditions in outlying districts was 
obtained from the Fluorine mine, on Copper Mountain. Tunnels were driven in 
granite extending underneath the workings of the Fluorine mine, and much gas was 
said to have issued from the surrounding rocks in these workings. 

UNDERGROUND TEMPERATURE. 

No accurate measurements have been undertaken to ascertain the exact 
increment of temperature with depth in the Cripple Creek district. A few observa¬ 
tions are, however, available which may serve to.attain at least an approximate 
result. 

Concerning the mean annual temperature at Cripple Creek, which should be 
approximately identical with the rock temperature at the depth of, say, 50 feet, it 
should be stated that the only data available are incomplete records at Cripple 
Creek extending over a period of three years. By estimating temperatures for 
those months which are lacking the figure of +42° F. is obtained for Cripple Creek, 
the probable error being about +2°. The mean annual temperature at Colorado 
Springs is +47° F., while that of the summit of Pikes Peak is 19.4°. The determina¬ 
tion for Colorado Springs is based on the average for twenty-six years and that for 
Pikes Peak on records for fifteen years. 

Cripple Creek has an elevation of about 9,000 feet, while the elevation of Colo¬ 
rado Springs approximates 6,000 and that of Pikes Peak 14,000 feet. At the eleva¬ 
tion of 10,250 feet in the vicinity of Cripple Creek a mean annual temperature of 
+ 41° F. ha,s been assumed. 

13001— No. 54—06-19 


270 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


The Last Dollar mine is 1,200 feet deep, the shaft having a surface elevation of 
10,278 feet. In a long crosscut on the 1,200-foot level, under the Modoc vein, a 
temperature of +16° C. ( + 60.8° F.) was measured at the breast. This figure is 
doubtless not far removed from the actual temperature of the surrounding rock. On 
the assumption that the mean surface temperature is 41° F., this will correspond to 
an increment of 1° F. per 58 feet. In the same mine and on the same level the 
temperature in the stopes 40 feet above the rail was found to be +17.5° C. (+ 63.5° 
F.), which is probably higher than the normal temperature. At the shaft on the 
same level the temperature was 4- 13° C. 

The next observations were taken in the Vindicator mine, at the breast of the 
Christmas crosscut, 800 feet below the surface, the elevation of the collar of the 
shaft being 10,209 feet. The temperature obtained at the breast of the crosscut 
was +12° C. ( + 53.6° F.). Again assuming that the mean surface temperature is 
41° F. and that the temperature of the crosscut does not differ materially from that 
of the surrounding rock, we obtain an increment of 1° F. per 63.5 feet. 

The Ophelia tunnel extends for over 7,000 feet westward from Cripple Creek 
into the heart of the district. At the time of visit work had been discontinued at 
the breast for several months. Connection with the surface was established through 
the Callie shaft, 1,800 feet back from the breast. Xo artificial ventilation was 
resorted to, and it may again be assumed that the temperature at the breast does not 
differ more than 1° or 2° at most from the temperature of the surrounding rocks. On 
March 18, 1904, the temperature at the breast was + 12° C. ( + 54° F.). The vertical 
distance to the surface being 700 feet, and a mean annual temperature of 41.3° F. 
being assumed for that surface elevation, an increment of 1° F. per 55 feet is obtained. 

At the Conundrum mine, in the workings on level 6, 750 feet below the surface, 
a temperature of +53° F. was measured on March 21, 1904. There was some venti¬ 
lation at the time, and it is possible that the figures may be somewhat too low to 
represent the actual rock temperature. If we assume that it is approximately 
correct, however, the increment is calculated to be 1° F. per 60 feet. 

This is in some measure confirmed by the observed temperature of the water 
where it issues from the El Paso drainage tunnel, the portal of which has an elevation 
of 8,783 feet. This temperature was found to be +14° C. ( + 57.2° F.). Assuming 
that this water is drained from an average level of 1,000 feet below the surface 
throughout the large area affected by the tunnel and further that the mean annual 
temperature is +41° F., we obtain an increment of 1° F. per 62 feet. 

Although these observations are not accurate, they may be depended on as 
showing that the average increment of temperature in the Cripple Creek district 
approximates 1° F. per 60 feet. This is very nearly the normal figure usually given 
for the increase of temperature in depth and indicates that there is no special source 
of heat present which would interfere with mining at depths much greater that those 
attained at present. At the depth of 2,400 feet a temperature of +81° F. might be 
expected if the rate is maintained. At 3,600 feet the temperature should rise to 
101° F. 

As has been explained in more detail in the paragraphs devoted to subterranean 
gases, a higher temperature obtains at places where mine gases are especially 
abundant. 


PART II.-DETAILED DESCRIPTIONS OF MINES. 


CHAPTER I.—MINES NORTH AND EAST OF THE TOWN OF 

CRIPPLE CREEK. 


MINERAL IIILL. 

The southern slope of Mineral Hill contains a great number of prospects, on 
some of which much work has been done, though all operations were suspended in 
1903. These prospects are almost wholly confined to the area covered by breccia. 
The rock shows strong evidence of mineralization in places, being bleached and 
impregnated by carbonates and pyrite. The Roanoke shaft is located pn the 
reservoir ridge immediately north of the town, and sunk to a depth of 375 feet, 
water now standing 308 feet below the collar. It is reported that a well-defined 
north-south vein was encountered, containing some ore. A little higher up are 
the Sunflower shafts, each 100 feet deep, with about 800 feet of drifts.® Still 
farther north and about 200 feet vertically below the summit are the Laura Lee 
and Addie C. shafts, the former 100 feet, the latter considerably deeper—458 feet, 
according to report. Some quartz containing native gold is said to have been 
found in the Laura Lee. 

CARBONATE HILL. 

Carbonate Hill rises a short distance east of Mineral Hill. Its summit is made 
up of granite, while volcanic breccia covers its southwestern slopes. Like Mineral 
Hill, its slopes are dotted with prospect holes, but thus far little of permanent value 
has resulted. Near the summit is a phonolite dike, in and near which some oxi¬ 
dized ore has been found. On the southwestern slope the Elkhorn mine is located, 
in breccia. High-grade ore has been shipped from this property at intervals. The 
shaft is 450 feet deep. Toward the east the breccia extends across the gulch and 
covers the western and southern parts of Tenderfoot Hill, but the productive area 
is not encountered until the slopes of Poverty Gulch are reached. 

POVERTY GULCH. 

Poverty Gulch, heading at Hoosier Pass, separates Tenderfoot and Globe hills 
and extends down into the town of Cripple Creek. Its upper course lies over 
breccia containing some dikes of phonolite, latite-phonolite, and basalt, but a short 
distance below the C. O. D. mine it enters the schist and gneiss areas. Dikes and 
principal veins trend north-northeast or northwest, the former system being the 
most productive. The Gold King basic dike is of remarkable length and evidently 


a Hills, Fred, Official Manual of the Cripple Creek District, 1900. 


271 



272 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

somewhat mineralized throughout. Many of the lodes are of short horizontal 
extent and not always persistent in depth. The three most important mines are 
the Abe Lincoln, C. O. D., and Gold King. The latter was the first regularly pro¬ 
ducing mine in Cripple Creek. In 1904 only the first-named was actively worked. 

C. O. D. MINE. 

The C. O. D. mine, operated by the Rebecca Gold Mining Company, is one of 
the oldest mines of the district. In 1894, when Penrose examined it, the depth 
attained was 220 feet. At the present time the shaft is 800 feet deep, ten levels are 
turned, and the total developments consist of about 4,000 feet of drifts, extending 
chiefly northward, level 8 attaining a distance of 600 feet from the shaft. The 
elevation of the collar is 9,821 feet. Except in a very limited way by lessees, the 
mine was not worked in 1903 or 1904. The bottom was dry in the latter year. 
The total production is given as $594,000, and the dividends amount to about 
$150,000. The C. O. D. vein is contained in normal fine-grained breccia, with a 
moderate amount of disseminated pyrite and carbonates. Level 7 is said to run 
out in schist 130 feet south of the shaft. A crosscut, 300 feet long, toward the 
east on level 8, remains throughout in breccia. The vein is a sharply defined fissure 
striking about N. 10° E., and dipping about 84° in an east by south direction. 
The Gold King vein is said to have been cut in a crosscut on level 5 about 200 feet 
west of the shaft. The crosscut east on level 8 cuts two veins 200 and 300 feet 
distant from the C. O. D. and approximately parallel to it. Both are oxidized and 
show no pay ore. One of them is believed to represent the extension of the Proper 
vein. The ore in the C. O. D. is of the usual type, with calaverite, quartz, and 
fluorite. Fresh tellurides were found close to the surface. Much of the ore aver¬ 
aged 5 ounces per ton. A small cross seam containing tetrahedrite was struck on 
level 10 and is reported to have yielded assays of 850 ounces silver and 5 ounces 
gold per ton. 

Penrose says of the upper levels that the vein is a well-defined fault fissure, 
with grooves and slickensides, and with numerous subordinate cracks on either side 
of the main fissure. On level 8, where seen in 1904, the vein is marked by several 
narrow fissures and has the ordinary appearance of the sheeted zones character¬ 
istic of Cripple Creek veins. In one place the vein is slightly faulted by cross 
seams. From the discovery shaft to level 6 the ore shoot pitched southward 
toward the main shaft at an angle of 40°. Its length along the levels was about 100 
feet. Below, this point its pitch became reversed toward the north, but at the 
same time became much poorer. Near the main shaft ore was stoped from level 
8 to level 6, but the ore seams are said to have been narrow, at the same time spread¬ 
ing over a wider space. On levels 9 and 10 little if an} T ore has been stoped. 

PROSPECTS NEAR THE C. O. D. 

The partly oxidized breccia near the C. O. D. and close to the contact with 
the schist contains many little seams of fluorite and quartz. Much of the surface 
material is rich enough for shipment, but none of these deposits has proved to be 
of great extent. 


MINES OF POVERTY GULCH. 


273 


The Proper vein cuts through breccia about 200 feet above the C. O. D. on the 
south side of Poverty Gulch, and is developed by an incline shaft with a vertical 
depth of 100 feet. A dike of latite-phonolite about 30 feet wide is exposed on two 
levels apparently trending southwesterly toward the Gold King mine. The vein 
strikes northeastward and dips to the southeast. A small shoot from which a car¬ 
load of 2-ounce ore has been shipped outcrops near the shaft. Stringers of galena 
and zinc blende occur in the ore. 

GOLD KING MINE. 

The Gold King mine, also known as the El Paso Gold King, operated by the 
Gold King Gold Mining Company, is situated a few hundred feet north of the C. O. D., 
on the northwest side of Poverty Gulch. It was the earliest regular producer and 
has been actively worked up to a recent date. In 1904 it was idle and not accessi¬ 
ble, but a reopening of the mine was under consideration. The dividends distrib¬ 
uted up to July, 1901, are given in Hill’s Manual as $262,000. The ground owned 
comprises 40 acres. 

The mine is developed by a vertical shaft 1,007 feet deep; the elevation of the 
collar is 9,852 feet. Nine levels are turned and extend chiefly northward from the 
shaft. The total length of drifts and crosscuts is about 2 miles. Level 9 (the 
deepest) is 840 feet below the collar. Water has been a great source of trouble and 
expense. The operations have been suspended until the El Paso tunnel (elevation 
8,790 feet) shall have drained level 9. The water level stood 875 feet below the 
collar in March, 1904. 

The country rock is normal fine-grained breccia, with some disseminated 
pyrite and carbonate (ankerite). The main vein is said to follow a plionolite dike 
trending N. 10° E. A very persistent basic dike, probably a monchiquite, also 
exposed in the Abe Lincoln workings, lies 250 feet west of the shaft and has been 
drifted on for several hundred feet on levels 3, 5, and 8. It is 3 to 5 feet wide. 
Three ore-bearing veins are known on the property. The first and most important 
trends N. 10° E. from the shaft and has a very steep east-southeast dip. Drifts 
are extended on it on all levels for about 400 feet north of the shaft; south of it 
some exploration has been done on levels 1, 5, and 8. A second nearly vertical 
vein, trending north-northwest from near the shaft and intersecting the first just 
south of it, has been developed on the adit and first levels for a distance of 300 feet, 
but has not been found productive. Four hundred feet north of the shaft it would 
intersect the third vein, which follows the basaltic dike mentioned above. Like 
the dike it strikes N. 30° E. and dips 70° west-northwest. Some fluorite and cala- 
verite ore occurred on it, but the vein proved productive only down to level 5. It has 
been opened on levels 3, 5, and 8. 

The ore is of the usual kind, the calaverite being accompanied by quartz and 
fluorite in all of the veins. There is little oxidation, unaltered tellurides being 
found close to the surface. Galena, zinc blende, and tetrahedrite are reported 
absent. A small vein in the northern part of the mine, 40 feet east of the basalt 
dike, contained much galena, but no work was done on it. 


274 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

The pay shoot on the main vein, from which the largest part of the production 
has been derived,.has a maximum horizontal length of 300 feet and from the vicinity 
of the shaft pitches steeply north on the plane of the vein. The width of ore is 
very variable, ranging on level 8, for instance, from 1 to 28 feet. The ore is reported 
to continue down to the deepest (ninth) level. The pay shoot on the vein follow¬ 
ing the basic dike is situated about 400 feet north of the main shaft; it seems to 
pitch steeply northward, but, as stated, proved productive only down to level 5. 

MOLLIE KATHLEEN MINE. 

The Mollie Kathleen mine is situated on the south spur of Tenderfoot Ilill, just 
north of the El Paso Gold King mine. It is owned by Hr. M. C. Gortner, of Cripple 
Creek, and is at present being operated under lease by the Creston Big Eight Mining 
Company. The total production is estimated at $200,000. The underground 
developments consist of a shaft 700 feet deep, with stations cut at 100-foot intervals 
and levels at 200 and 700 feet. 

The main shaft and the greater portion of the workings are in a dense breccia, 
considerably pyritized and in places partially oxidized. On the 700-foot level, 
however, the workings to the northwest, beginning at a point about 75 feet from 
the shaft, are in a pyritized massive rock which proves to be a syenite. The con¬ 
tact could not be located exactly, but rock is probably of intrusive character. On 
the 200-foot level a phonolite dike 10 feet wide, striking about N. 25° E. and approx¬ 
imately vertical, occurs 50 feet northeast of the shaft. It was not observed on the 
lower level, but a dike of phonolite apparently vertical and about parallel with the 
drift to the northwest occurs near the shaft on the 700-foot level. 

The Gold King basalt dike, striking on the average about N. 35° E. and dipping 
75° NW., is cut on the 200-foot level about 150 feet northwest of the shaft. On 
the 700-foot level the dip has carried it about 250 feet from the shaft. The dike 
is somewhat irregular in dip and strike, and varies in width from 3 to 5 feet. About 
150 feet northwest of the shaft, on the 200-foot level, the dike is faulted about 1 
foot by a fissure running N. 40° W. and dipping about 65° SW. Neither the fault 
nor any well-defined fissure which might represent it was observed on the 700-foot 
level. On the upper level the dike is considerably decomposed, but shows the 
characteristic longitudinal parting or jointing and the narrow seams of carbonates 
as distinctly as on the level below. 

A number of more or less persistent veins have been found belonging to two 
systems, one of them with a northeasterly, the other with a northwesterly strike. 
The main vein of the Gold King, striking about N. 10° E., has not been encountered 
in this mine. The most important vein apparently follows the basic dike of the 
Gold King, which has been cut and drifted on at both levels. 

On the 200-foot level a zone of Assuring is encountered about 150 feet north¬ 
west of the shaft. It strikes N. 60° E. and dips 75° to 80° NW. The lode ranges 
from 4 to 7 feet in width and consists of very many narrow fissures or cracks approx¬ 
imately parallel, but of little persistence. The breccia immediately about the 
fissures is oxidized. The lode carries values, but in most places the}’ are too low 
to permit of profitable working. Tellurides are said to occur both in the seams 
and, more sparingly, in the rock between them. 


MINES OF POVERTY GULCH. 


275 


The lode is crossed, northeast of the shaft, by the Gold King basalt dike. On 
this level the course of the dike is about N. 50° K., so that here the dike and lode 
intersect at an acute angle. The lode, in fact, seems to follow the dike for 20 feet 
or more. Sixty or seventy feet southwest of this junction the lode and dike approach 
again. At both points good ore occurs. 

On the 700-foot level the course of the basalt dike is N. 30° E. It is somewhat 
fresher than above. Low values are said to occur all along the dike at this level, 
but no stoping has been done. Nothing was seen which corresponded to the 
northeast lode on the upper level. About 150 feet northwest of the shaft on the 
700-foot level a narrow vein running northeast and dipping steeply northwest has 
been cut at two points. The vein is characterized by a quartz filling with vugs, 
carrying in places considerable quantities of pyrite, with sphalerite and a little 
galena, also low values in gold and silver. It evidently corresponds to the vein 
containing galena described from the Gold King mine. 

A number of northwesterly trending fissures have been found, but they seem 
to carry small values. On the 200-foot level a lode has been cut about 100 feet 
northeast of the shaft and drifted on for 400 feet. It strikes N. 55° W., dips 75° 
NE., consists of a number of narrow, rudely parallel fissures in breccia. This lode 
has furnished a small pocket of ore. It was not found on the 700-foot level. Three 
hundred feet northeast of the shaft on the bottom level a similar fissure zone was 
encountered and drifted upon. It contained a small bunch of ore. 

Two parallel fissures 3 to 12 inches wide and about 8 feet apart, running north¬ 
west and dipping about 80° NE., are cut 200 and again 250 feet west-northwest of 
the shaft. They are partly filled with large and small loose fragments, mostly 
oxidized, and appear to be old watercourses. They are barren. 

Just west of the shaft on this level a short drift has been run on a narrow 
northwest seam carrying soft, clay-like matter, considerable pyrite, a little galena, 
and very small quantities of gold. 

The greatest amount of ore was shipped from shallow workings on the Gold 
King basalt dike. This was stoped for practically the whole width of the claim 
down to a depth of about 75 feet, a point where at that time (1894-95) water 
interfered. Although the hill has since been drained to a lower level, mining has 
not been resumed in these upper workings 

The junction of the basalt dike and the northeast' lode on the 200-foot level 
made ore which has been stoped 20 to 30 feet high, about 60 feet long, and 4 to 6 
feet wide. Values did not warrant further stoping. To the south of the junction, 
where the lode and dike approach, a stope had only been begun at time of visit, so 
that the form and extent of that ore shoot could not be determined. 

GOLD PASS DIKE. 

The narrow, irregular, and sometimes interrupted Gold Pass dike is cut by the 
Chicago and Cripple Creek tunnel 1,300 feet from its portal, and has been followed 
500 feet toward the northwest and 700 feet in a southeasterly direction. It seems 
to be slightly mineralized throughout, but on the tunnel level the only stopes 
opened are at the end of the north drift and at the intersection with a vein supposed 
to be the Half Moon, 500 feet southeast of the tunnel. The Nolan shaft connects the 



276 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

tunnel level with the surface, 400 feet above. At a height of 140 feet above the 
tunnel some ore is stoped at present along this dike. A small vein with a north¬ 
westerly course is traceable for a distance of 400 feet on the surface, but the basaltic 
dike does not show very clearly. The ore consists of thin quartz seams with cala- 
verite contained in breccia or basaltic* rock. The property belongs to the Stratton 
estate. 

ABE LINCOLN MINE. 

INTRODUCTION. 

The Abe Lincoln claim in Poverty Gulch, near the eastern edge of the town of 
Cripple Creek, was located in April, 1895, and the mine began to ship ore the same 
year. The property is now part of the Stratton estate and is worked under lease. 
The total production is unknown. In 1903 and 1904 the mine was actively worked 
and shipped about 30 tons per day. 

UNDERGROUND DEVELOPMENT. 

The Abe Lincoln is operated through a vertical shaft, 600 feet in depth, with 
three levels, 360, 500, and 596 feet, respectively, below the collar. The collar of 
the shaft is 9,611 feet above sea level. There are some smaller shafts on the prop¬ 
erty, of which the most important is the Arcadia, 160 feet west-southwest of the 
Abe Lincoln shaft. The Arcadia has three small levels, all above the 360-foot Abe 
Lincoln level. A large amount of horizontal development work has been done on 
levels 1 and 2. On level 1 a north crosscut extends for 750 feet from the shaft, 
well under Womack Hill. Another crosscut extends northeast of the shaft for 
900 feet to a point nearly under the portal of the Chicago tunnel, where it connects 
with a long northwest-southeast drift. Level 1 also extends about 1,000 feet 
southwest of the shaft, partly as drift and partly as crosscut. On level 2 are a 
number of drifts and crosscuts extending for about 500 feet southwest of the shaft, 
a northeast crosscut of about 400 feet to the May Queen lode, and an east crosscut 
about 2,000 feet in length toward the Gold Pass shaft. The development on level 
3 is less extensive than on the others and is entirely to the southwest of the shaft. 

GEOLOGICAL FEATURES. 

The workings of the Abe Lincoln are partly in the granite, gneiss, and schist 
complex underlying the town of Cripple Creek and partly in the breccia. The 
productive part of the mine, however, is entirely in the older rocks. The contact 
between the gneiss and breccia is usually fairly well defined, though the gneiss 
shows more or less local brecciation and the breccia near the contact contains 
abundant gneiss fragments. The contact exhibits some pvritic mineralization, but 
no ore, and has not been much explored. The general dip of the contact is south¬ 
easterly. From the surface to level 1 the angle of dip appears to be 80° or 85°. 
Below this the dip is evidently lower, the relative positions of the contact on the 
two levels indicating an angle of about 30°. Most of the ore occurs in a fine-grained 
granitic gneiss such as is exposed at the surface near the Midland station, in many 
of the street cuts in Cripple Creek, and on the dump of the Cripple Creek Enter¬ 
prise shaft, opposite the hotel. The gneissic structure, however, is somewhat less 


MINES OF POVERTY GULCH. 


277 


conspicuous in the Abe Lincoln mine than elsewhere. This gneiss is cut by irregular 
dikes of reddish granite, such as may be seen in the cut at the Short Line station 
in Cripple Creek, and by dikes of phonolite. So far as known these dikes have 
exerted no particular influence on ore deposition. The schist encountered in the 
mine is a fibrolitic schist similar to that exposed in the Short Line cut near the 
Poverty Gulch trestle, containing large scales of muscovite. It is often intimately 
mingled with the gneiss, and like the latter is cut by dikes of red granite. The 
long east crosscut on level 2, after passing through breccia, continues for about 
250 feet in shattered schist, which contains much pvrite in veinlets and in dissemi¬ 
nated crystals. This schist is part of the same mass that is exposed at the surface 
near Fairview and that is reached also by the Chicago and Anaconda adits. 

In nearly all the breccia seen in the Abe Lincoln mine granitic or gneissic 
fragments predominate over those of other rocks. In a few places, however, 
fragments of schist are the most abundant. Recognizable fragments of phonolite 
or andesite are extremely rare. The breccia usually contains much pyrite as finely 
disseminated crystals and in irregular bunches and veinlets. 

There are at least two important basic dikes in the Abe Lincoln mine. One 
of these, called the Gold King dike, is supposed to be the dike known in the Gold 
King mine in Poverty Gulch and exposed beside the Short Line track just south¬ 
west of that mine. It has been followed for 500 feet in the Chicago tunnel, for 
about 70 feet on level 1 of the Abe Lincoln, and for 600 feet on level 2, where it lies 
about 1,000 feet east of the Abe Lincoln shaft. Its general course is N. 10° E. and 
it dips west at from 60° to 75°. This dike is crossed by a second basic dike which 
strikes generally N. 75° W. and dips southwest at varying angles, ranging from 
about 60° to 75°. This second dike has been followed for about 700 feet on level 1 
of the Abe Lincoln, in a drift which is under and has nearly the same course as the 
initial portion of the Chicago tunnel. Both dikes appear to have been intruded at 
the same time and there is no appreciable faulting at the junction. The second 
dike, known as the Gold Pass dike, is supposed to be identical with the basic dike 
which has been drifted on for over 1,300 feet in the Chicago tunnel near the Gold 
Pass shaft. The general strike of the dike, as shown bj^ this Gold Pass drift, is 
northwest. But as its course is very irregular and as it frequently branches and 
pinches out it may be that the two dikes, or rather dike zones, are really continuous. 

LODE SYSTEMS. 

Most of the ore in the Abe Lincoln mine occurs in a network of narrow and not 
verc persistent lodes in gneiss, southwest of the main shaft. The most prominent 
of these lodes strike northwest or notheast, but they are intimately associated 
with other fissure zones running more nearly north and south. Few of the individual 
fissure zones have been followed for more than 400 feet. The most persistent 
productive lode is the Lillie, which strikes N. 20° E. and has been stoped for a 
length of 300 feet on level 1. On level 2, however, the Lillie fissure zone has not 
been found. The Abe Lincoln lode is a sheeted zone of rather indefinite width, 
striking N. 50° or 60° W. and dipping southwest. The name is used to designate 
one or more fissures of a general zone of approximately parallel fissures. The total 
width of this zone is probably 150 or 200 feet. The portion known as the Abe 


278 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

Lincoln vein varies, according to circumstances, from a few inches to 30 feet in 
width. 

The gneiss is cut also by a number of nearly horizontal fissures with generally 
southerly dip. These fissures, as well as the more nearly vertical lodes, have 
influenced the deposition of ore, as will presently be shown. 

CHARACTER OF ORE. 

The essential constituent of the Abe Lincoln ore is calaverite, which occurs 
with quartz in little vuggy fissures in the gneiss. Fluorite occurs occasionally 
with the quartz. Some of the veinlets on level 3 contain galena, pyrite, and tetra- 
hedrite intimately associated with the pyrite. As a rule pyrite formed first, then 
tetrahedrite (when present), and finally quartz and calaverite. The galena appar¬ 
ently formed at about the same time as the quartz and calaverite, but is of sporadic 
occurrence. The ore on levels 1 and 2 is said to have contained very little silver, 
but on level 3 ore containing G or 7 ounces of gold per ton carries as much as 2 
ounces of silver. No ore was seen at the time of visit on levels 1 and 2, but it is 
said to have been practically unoxidized. No oxidation was observed on level 3. 
The ore on levels 2 and 3 as mined in 1903 and 1904 is of medium grade. 

PAY SHOOTS AND LODE STRUCTURE. 

Some ore occurred in the Gold Pass basalt dike above level 1. It is said to 
have been rich, but was found in small isolated shoots of an aggregate length of 
about 500 feet. None of this ore was seen at the time of visit and its mineralogical 
character is not accurately known. It was probably partly oxidized. The Lillie 
lode contained a pay shoot which just above level 1 was about 300 feet in length. 
The ore occurred in the veinlets of a narrow sheeted zone in gneiss. So far as known, 
this pay shoot does not extend for more than a few feet below level 1, crosscuts on 
the lower levels having failed to find even a distinct continuation of the Assuring. 

The pay shoots visible at the time of visit all occur southeast of the shaft, at 
the intersection of two or more of the fissures in the gneiss, wliich are individually 
rather indistinct and seldom very persistent. Although the ore bodies at these 
intersections are of irregular form, yet the ore is confined to the actual fissures and 
to the accompanying irregular fractures, and does not, as in the Ajax, Thompson, 
and some other mines, permeate the granitic rock. These fissures are as a rule only 
a fraction of an inch in width. For a distance of half an inch or so from the fissure 
the gneiss contains disseminated pyrite and is greenish yellow in color. Beyond 
this narrow zone the gneiss is normally fresh and unaltered. The walls of the 
fissures are usually lined with a film of pyrite and upon this are deposited the quartz 
and calaverite, sometimes with tetrahedrite and galena. The fissures are in some 
cases of microscopic width and can be traced only by the narrow zone of greenish 
alteration in the gneiss, which is always an indication of the presence of ore. A 
typical ore body being opened at the time of visit on level 3 occurs at the inter¬ 
section of at least three distinct sets of fissures. One set strikes nearly north and 
dips east at about 75°. It forms a well-defined zone of sheeting from 6 to 20 feet 
in width. Another set strikes northwest and dips southwest at about 45°. The 


MINES OF RHYOLITE MOUNTAIN. 


279 


fissures of this zone are more widely spaced than the other, the whole zone being 
at least 30 feet in width. The ore occurs in the vicinity of the intersection of these 
two sets of fissures with a so-called “fiat vein” striking northwest and dipping 
northeast at 45° or 50°. This fiat vein is about 4 inches wide and consists of quartz, 
valencianite, and pyrite, these minerals apparently being a product of replacement 
of the surrounding rock. The pay shoot, so far as developed at the time of visit, 
follows this “fiat vein,” though the latter itself does not contain ore. The ore 
body as stoped in January, 1904, was about 60 feet long and from 6 to 20 feet wide. 

About 150 feet southwest of this place, or 200 feet southwest of the shaft, is 
another pay shoot known as the Arcadia shoot. This is an irregular chimney-like 
body of ore which has been stoped on all the levels. It occurs at the intersection 
of at least three nearly vertical fissure zones—one striking northwest, another 
north-northwest, and another northeast. According to the manager, Mr. Walter 
Swanson, these vertical fissures are crossed by a number of nearly horizontal fissures. 
The best ore occurs near these horizontal fissures. This ore body was lately reached 
by crosscutting on level 3. 

UNDERGROUND WATER. 

Water was first encountered in the Abe Lincoln shaft at a depth of 128 feet, or 
about 9,483 feet above sea level. The maximum flow of 500 gallons per minute 
was reached at a depth of 350 feet, but the Ophelia and Standard tunnels ultimately 
drained the mine. In sinking the shaft to level 3, in the winter of 1903, a little 
water was encountered near the new level, but this soon disappeared, probably as 
a result of the drainage by the El Paso tunnel. 

RHYOLITE MOUNTAIN. 

GEOLOGICAL FEATURES. 

Rhyolite Mountain, with an elevation of 10,771 feet, lies 2\ miles north of 
Cripple Creek and is separated from Mineral Hill by the deep trench of Spring Creek 
On its eastern side the Pikes Peak granite reaches nearly to the summit, but the 
western and northern slopes are covered by a volcanic breccia, with usually coarse 
fragments of brownish or dark-gray color. As a rule, it contains but little pyrite. 
A smaller area of breccia covers the southern slope of the adjacent Copper Mountain. 
It is similar in character, hut contains many large fragments of granite. There is 
some evidence that the breccia of Rhyolite Mountain is of local origin and formed 
in a volcanic neck underneath the summit. Several large and irregular areas of 
normal phonolite cover the southern slope of the hills and also occupy their summits. 
These masses of phonolite are in most places bordered by intrusive contacts. 

PROSPECTS ON RHYOLITE MOUNTAIN. 

At the eastern foot of the steep granitic slope of Rhyolite Mountain the Pay 
Rock claim is located. A shaft 80 feet deep was here sunk on a seam trending 
northwest and containing a little calaverite. The shaft was deepened to 300 feet, 
but, it is stated, without results. 

About 150 feet below the summit are the prospecting shafts of the Rhyolite 
Beacon Gold Mining Company, from many of which good assays are reported. In 


280 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


one place the granite contains disseminated secondary fluorite. The overlying 
breccia is locally converted to a soft yellowish-white kaolin rock. The principal 
shaft is 200 feet deep and sunk through 150 feet of dark-brown, fresh breccia. At 
that depth the granite was met, the sharp contact dipping 45° W. and showing a 
hummocky surface covered with clay. Near the contact the breccia contains seams 
and disseminated grains of calcite. Some good assays are reported from the upper 
part of the shaft. 

The Metallic tunnel is located at an elevation of 9,250 feet on the western slope 
of Rhyolite Mountain. It is 1,000 feet long and reported to be entirely in granite. 
Farther north, on Bernhard Creek, some prospecting operations have been carried 
on along phonolite dikes in granite. 

FLUORINE MINE. 

The Fluorine mine, owned by the Montreal Gold Mining and Milling Company, 
is situated halfway up the southern slope of Copper Mountain. It is now leased 
bj r the Sioux Falls and Cripple Creek Gold Mining Company, who have recently 
built a 100-ton cyanide mill to treat the ore. The mine is of interest as being the 
northernmost producer of the camp. The total production could not be definitely 
learned, but it is probably near $160,000. The workings consist of several shallow 
shafts and a tunnel 200 feet in length. The stoping from the tunnel reached nearly 
to the surface, and the roof has recently caved in, leaving a large open chamber. 

The mine is situated practically on the contact of phonolite, breccia, and 
granite. The phonolite overlies the breccia, which in turn lies flatly on the granite. 
The breccia is not extensive just at this point, however, and pinches out in the 
farthest workings, leaving the phonolite resting on the granite. The different rocks in 
the mine appear to have contained much pyrite, but are now completely oxidized. 
The breccia is rather granitic and contains numerous large granite fragments. 

Rich pockets were found in the breccia, and were mined out. At the present 
time practically the whole of the breccia and some of the granite in the mine is 
being taken out and treated by cyaniding without roasting. The value of the ore 
now mined ranges from $4 per ton up. In a pit on the eastern part of the claim 
some rhodochrosite with argentiferous galena and zinc blende was found in spaces 
of dissolution in the granite. A tunnel driven underneath the Fluorine mine is 
entirely in granite and failed to find ore. 

The Copper Mountain mine, situated just east of the Fluorine, shipped some 
ore in 1898, but the amount was not ascertained. It is developed by a shaft 200 
feet deep and drifts extending in a northwesterly direction on a vein in phonolite 
containing pyrite, galena, and zinc blende, with fluorite gangue. 

RED MOUNTAIN. 

GALENA MINE. 

The Galena mine, located on the slope of Red Mountain toward Spring Creek, 
is the only place in the area west and northwest of Cripple Creek where any notable 
amount of ore has been found. The mine is owned by the Iron Mountain Mining 
and Milling Company and is developed by an incline shaft 560 feet deep, extending 


U. S. GEOLOGICAL SURVEY 


I 


PROFESSIONAL PAPER NO. 54 PL. XXI 




B . PIKES PEAK, FROM SUMMIT OF BULL HILL. 
Town of Gillett in left middle-ground. 










MINES BETWEEN CAMERON AND GILLETT. 


281 


from the croppings down to the level of a tunnel 1,000 feet long, near the level of 
Spring Creek. The total production is reported to have amounted to $12,000. 
Hill’s Manual gives $6,000 up to 1900. Little work was being done in 1904. 

The vein is contained in Pikes Peak granite, near the northwesterly trending 
contact of the Spring Creek granite. Its continuation across Spring Creek would 
carry it into the area of olivine syenite. The vein follows in part a phonolite dike 
which at the croppings is only 4 inches wide and is said to carry values up to $20. 
The general strike is northwest and the dip is 35° NE. In depth the vein straightens 
and in the tunnel dips 50°, appearing here as a dark streak, 8 to 10 inches wide, of 
crushed and partly replaced granite containing fluorite with some pyrite. The 
assay values are low. The present workings are in a winze 165 feet above the 
tunnel level. The vein is here 10 inches wide and distinctly crustified, consisting 
of quartz, fluorite, manganiferous dolomite, galena, zinc blende, and pyrite. This 
ore is said to contain 8 to 10 ounces silver and 2 to 3 ounces gold per ton. The gold 
values are probably in calaverite, though tills mineral was not positively identified. 
The pay shoot which was found at the croppings appears to pitch southeasterly on 
the plane of the vein, and it is hoped that a further extension of the tunnel will 
intersect it. 

AREA BETWEEN CAMERON AND GIEEETT. 

GEOLOGICAL FEATURES. 

The little town of Cameron is situated at the northern base of Bull Hill, near 
the head of Grassy Creek. The low hills north of the town consist of schist, gneiss, 
and the two principal varieties of granite, in irregular areas. A small outlier of the 
main breccia area covers Galena Hill. Near its contact the granite is often brec- 
ciated or shattered. North of this extends a rolling granite plateau on which, 2 
miles farther north, the town of Gillett is located. Trachyte and Cow mountains 
rise southeast of Gillett to an elevation of 1,000 feet above the plateau. A series of 
more or less continuous phonolite dikes with a general northerly trend traverse the 
granite between Cameron and a point 1 mile west of Gillett. A number of prospects 
and one or two mines are contained within this belt. 

SUNSHINE MINE. 

Situated on the southeastern slope of Galena Hill the Sunshine is of interest as 
being farther to the northeast than any of the mines in the main volcanic area. It 
is owned by the Fort Pitt Mining Company, of Pittsburg, Pa. The total production, 
including the ore taken from the Sunshine vein in Sedan ground, was estimated at 
$25,000 in January, 1904. 

The developments consist of an incline shaft following the vein for about 400 
feet, and four levels, representing perhaps 2,000 feet of drifting, besides a number 
of shallow shafts on the apex of the vein. The Sedan shaft, which connects with 
levels 2 and 4, is 250 feet deep and vertical. The elevation of the collar of the 
incline shaft is 10,180 feet. 

Examined underground, the country rock appears to be a coarsely brecciated 
mass of granite and schist, both of which are oxidized and kaolinized. A 15-foot 
phonolite dike crosses the property from northwest to southeast, and dips south¬ 
west at about 45°. 


282 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


A vein follows the foot-wall side of the phonolite dike. On level 2 the vein is a 
shattered zone varying from a few inches to 2 or 3 feet in width and sometimes 
contracting to a narrow seam. In general the ore is oxidized and contains much 
kaolin, but pyrite occurs in some places. Toward the north end of this level cross 
seams are numerous and ordinarily strike north-northeast. So far as known they 
they contain no values. About 125 feet southeast of the shaft on level 2 the vein 
becomes obscure and can not be traced farther. A north-northeast seam is drifted 
on and is said to connect about 25 feet to the south with a vein parallel and similar 
in character to the vein above described. Whether these two veins are one and the 
same with an intervening jog or two separate veins connected by a cross fissure the 
evidence was not sufficient to determine. Level 3 shows the vein with much the 
same character as above. In the fourth (bottom) level the vein is less oxidized 
and contains kaolin and quartz in places, also much pyrite. 

To the south the phonolite dike forms the hanging wall of the vein, and about 
50 feet south of the shaft the vein seems to break up, sending a number of pyritized 
stringers into the dike. It is as }-et uncertain whether these stringers were mere 
spurs from a continuous vein or whether they eventually carried the vein through 
the dike. 

Down to level 3 the ore is oxidized. Assays alone distinguish that which is 
workable. There seems to be a fairly distinct separation in the range of values, 
however, and ore containing \\ ounces per ton is about the poorest that has been 
mined. Between levels 3 and 4, where the vein is more quartzose, some of the ore is 
unoxiclized, and where sufficiently rich, tellurides can be seen in little veinlets and 
seams, along with oxidized material. 

From the surface south of the shaft down to level 2 a pay shoot has been 
stoped 2 to 4 feet wide and 30 to 60 feet long, being widest near the surface. The 
stope continues for a short distance below level 2, but the vein soon touches the 
under surface of the dike, and this is said to limit the pay ore. The shoot pitches 
to the northwest, and is said to have furnished good ore. 

Another shoot, also pitching to the northwest, occurs about 35 feet south of 
the shaft on level 3. A stope 3 feet wide and 20 feet long is being carried upward. 
The values do not appear to extend below the level. When the shaft had reached 
a depth of about 30 feet below level 3 a small bunch of ore was found and seem¬ 
ingly corresponded in position to a partly interrupted continuation of the ore 
shoot on level 3. The bottom level is being driven to the north in hope of cutting 
this ore shoot, the supposition being that it pitches to the northwest, as do the 
others. No conditions decidedly influencing the position of the ore shoots could 
be ascertained. 

DEPOSITS NEAR GILLETT. 

A number of prospects have been opened on small phonolite dikes north of 
the Sunshine mine. One of these, called the “E. F. C.,” is located on a hill just 
south of the main road between Cripple Creek and Gillett, II miles south-southwest 
of the latter town. The ore, which contains much galena and zinc blende with 
adularia, is found in the granite close to the wall of a phonolite dike, and is said to 
contain up to $40 per ton. 


MINES OF GLOBE HILL. 


283 


A little farther north, on the main road, is the Mayflower, the vein of which 
follows an east-west dike, and is said to have produced some good ore. The Bolivar, 
about 1 mile west of Gillett, is located on one of the principal phonolite dikes. 
Here, too, galena is said to occur. 

One mile west' of Gillett a number of northwesterly trending flat phonolite 
dikes cut the granite. The property of the Lincoln Mines Mining and Milling 
Company is located here. Small shipments amounting to about $4,000 have been 
made. The mine is developed by a vertical shaft 300 feet deep, and three levels, 
75, 160, and 300 feet below the collar, have been turned. The ore shipped is said 
to have been extracted from a northeast vein dipping steeply northwest; on the 
lowest level this vein does not appear, and it has possibly been deviated by a 
phonolite dike dipping 30° SW. A short distance westward is the Normandy shaft, 
200 feet deep, intersecting a phonolite dike, and the Hawkeye, sunk on a brecciated 
dike containing much fluorite. Close by the Hawkeye a narrow basic dike of 
doubtful original character is met trending southwesterly, and is said to contain 
some values. 

About half a mile east of Gillett, at the Great Western claim, a northeasterly 
trending zone with small seams of fluorite has been opened, and is said to contain 
low-grade ore. Some prospecting has been done on phonolite dikes at the southern 
point of Trachyte Mountain. A long tunnel is being driven under the summit of this 
mountain through granite in the hope of striking the supposedly mineralized vent 
connected with the mass of phonolite which covers its top. 

A number of small shafts and tunnels are located on the western slope of 
Cow Mountain, east of Trachyte Mountain, and low-grade ore is reported from 
some of these places. 

(JIjOIJE IIILiIi. 

GEOLOGICAL FEATURES. 

Globe Hill rises on the southeast side of Povertv Gulch to an elevation of 

•/ 

about 10,450 feet, and its broad, gently rounded summit overlooks the town of 
Cripple Creek. It is composed of volcanic breccia of normal type, but throughout 
very much oxidized and containing much limonite and kaolin. Dikes are notably 
absent. The rock is extremel}' shattered by seams and short veins, having many 
different directions and dips and often filled with quartz. The adjoining western 
part of Ironclad Hill is geologically similar to Globe Hill, but contains a number of 
strong veins with northeasterly trend and characterized by well-crystallized smoky 
comb quartz. Here, too, the breccia is thoroughly oxidized over a considerable 
space, and this oxidation descends at least 700 feet to the level of the Chicago 
drainage tunnel. Nothing similar to this deep and extensive oxidation of the 
rock occurs in any other part of the district. It has been assumed by Penrose and 
Rickard, who have described these occurrences, that they are due to the decom¬ 
posing action of thermal waters. In a general way this is probably correct. (See 
p. 284.) Ironclad Hill, like Globe Hill, is characterized rather by irregular masses 
of low-grade ore chiefly confined to the surface than by large ore shoots following 
the veins. 


284 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

DEERHORN MINE. 

The Deerhorn mine, which occupies the summit of Globe Hill, is owned by 
the Stratton estate. A considerable quantity of ore has been extracted from the 
property, chiefly from the open cuts, but no exact figures could be obtained. The 
developments comprise several large open cuts underneath which the Globe tunnel 
(elevation of portal about 10,325 feet) extends in many ramifications. The deeper 
developments start from the Deerhorn shaft (elevation of collar about 10,425 feet), 
which is 575 feet deep. Six levels are turned and exploratory drifts extend 600 or 
700 feet' in various directions, chiefly north, south, and west. Level 6, 565 feet 
below the collar, has several long crosscuts in various directions and connects 
with the Plymouth Rock shaft, 650 feet to the southwest; the various drifts and 
crosscuts will aggregate nearly 2 miles. 

The soft oxidized breccia on top of Globe Hill contains small values throughout 
and many smaller shoots and pockets of richer ore. Values of about $5 per ton 
are said to be widely distributed, and parts of the oxidized material would probably 
be suitable for the direct cyanide process without roasting. In the Globe tunnel, 
which throughout traverses the oxidized breccia filled with kaolin and limonite, 
the first 300 feet are reliably reported to average $3 per ton. Some of the seams 
cany up to SI5. A few hundred feet from the portal are old workings, the ore 
of which is said to average SS across a width of 100 feet, while along some fissures 
it will average S30. There are few quartz veins; the numerous seams and veinlets 
appear nonpersistent; occasionally they contain partly decomposed fluorite. Much 
ore was extracted from the large pit 200 feet north of the shaft. The breccia is 
ordinarily entirely decomposed, but a few masses of bluish, less oxidized, rock 
occur; these, however, are said to contain very low values. Seams cut the mass 
in many directions; one system dips 10° to 40° S.; another north-south system is 
vertical. A large mass of this rock is said to average $25 to $30, and connects with 
a smaller shoot on the Globe tunnel level, forming a large body which dips south 
or southwest. The flat seams sometimes cut off the ore. 

The lower levels were not accessible, and no work was being done on them. 
On level 6 a drift running out west-northwest is said to follow a “soft fluorite vein 
20 feet wide.” On the whole the results of the extensive underground exploration 
are said to have been disappointing, though some rich seams are reported from 
various places. The oxidation extends to the bottom level, and is said to be as 
well marked here as near the surface. 

The large masses of gypsum found near the shaft are of particular interest. 
They are mentioned by Penrose in his report and more fully described by T. A. 
Rickard,® who says that at a depth of 240 feet the shaft cuts into a mass of gypsum, 
which continues for about 300 feet to the bottom level. There are at least three 
of these chimneys, ending with narrow points a short distance above level 3; the 
largest is at least 75 feet in diameter near the bottom of the shaft. The gypsum 
is compact, white, and crystalline; it contains grains of pyrites and a little dis¬ 
seminated fluorite, as is well shown on the dump of the shaft. Mr. Rickard says 
that “The surrounding breccia is everywhere traversed by color bands due to 


a Trans. Am. Inst. Min. Eng., vol. 30, 1900, p. 399. 








MINES OF GLOBE HILL. 


285 


layers of gypsum, manganese, oxide, and iron ocher. Scattered through the vicin¬ 
ity but parallel to the group of columns of gypsum there are patches as well as 
seams of fluorite sand, consisting of particles of crystalline silica, stained purple by 
admixture with fluor-spar. The upper levels also show bands of * * * pure 

kaolin.” For further discussion in regard to this occurrence see page 220. 

PLYMOUTH ROCK MINE. 

The Plymouth Rock property, likewise owned by the Stratton estate, is 
located on the west side of Ironclad Hill, about 600 feet southwest of the Deerhorn 
shaft. The production is not known. Developments consist of a shaft between 
800 and 900 feet deep, the principal workings being on a northeasterly trending 
vein, possibly the same as the Ironclad. From the lowest (ninth) level drifts 
extend for a couple of hundred feet west, northeast, and southeast. The shaft 
and workings, which were inaccessible in 1904, are reported to be throughout in 
thoroughly oxidized breccia. The deep exploration is said to have failed to develop 
any ore bodies, though much of the soft rock gives traces or very low assay values 
in gold. 

The Chicago tunnel, the elevation of which is about 9,700 feet, extends from 
Poverty Gulch to the Plymouth Rock shaft, with which it connects about 700 feet 
below the surface. The tunnel extends for 2,000 feet in an east-southeast direction, 
and then changes to a few degrees north of east and continues for about 2,200 feet 
farther, to the connection with the shaft. From its portal to the end the tunnel 
traverses normal breccia and aside from the few basalt dikes cut in the first 1,200 
feet there are no intrusive masses present. The breccia is in general not oxidized 
and contains a little pyrite. A specimen from a point 1,200 feet from the shaft 
consists of normal fine-grained breccia of phonolite and granite, with much finely 
distributed pyrite. The ferromagnesian silicates have been converted to cliloritic 
material. Otherwise there is little alteration. About 1,000 feet from the end 
the rock within a short space becomes entirely oxidized and softened; it is filled 
with kaolin, limonite, and oxides of manganese; sometimes it also contains gypsum. 
At the end the rock is extremely soft, and close timbering is necessary. There are 
no distinct veins, but seams, usually with much kaolin, run in various directions. 
The rock is said to contain small assay values throughout, ranging up to SI.50 
per ton in gold. Branch drifts from the main tunnel enter schist. 

A thousand feet east-northeast of Plymouth Rock shaft is the World’s Fair 
claim, also belonging to the Stratton estate. A shaft about 200 feet deep has been 
sunk on it and some drifting has been done on a northerly trending vein. A little 
ore is said to have been shipped. 

IRONCLAD MINE. 

The Ironclad mine is situated a few hundred feet southwest of the Plymouth 
Rock and is operated at present by the Cripple Creek Homestake Mining and Reduc¬ 
tion Company. The total production is stated to be 8225,000. A considerable 
amount of low-grade oxidized ore has lately been encountered on the claims adjoin¬ 
ing the Ironclad on the southeast; this ore is at present mined and milled by the 
same company, the process employed being that of simple cyaniding without 

13001— No. 54—06-20 



286 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


roasting. In 1904 a 150-ton mill was in operation, but a much larger one is now 
(1905) in course of construction. The Ironclad mine is developed by a vertical shaft 
690 feet deep, with seven levels, and at least 1,500 feet of drifts and crosscuts. The 
elevation of the collar is about 10,425 feet. Level 7 is 660 feet below the collar. 

The country rock consists throughout of thoroughly oxidized breccia of normal 
type. Above level 4 the ore bodies consist of irregular masses of soft, oxidized 
breccia, with many small seams of comb quartz showing radial structure. On 
level 4 a well-defined vein begins to appear, striking northeasterly and dipping 
about 70°'SE.; the same vein has been reached by crosscuts on all of the lower 
levels; it is from 1 to 6 feet wide and consists chiefly of soft, brown, clayey vein 
matter, with seams of comb quartz. No tellurides remain; copper stains are often 
found, and a specimen from between levels 6 and 7 contained a little tetrahedrite, 
with chrysocolla, the former inclosed in quartz. Fluorite seems to be absent or 
entirely decomposed in the main vein, but near the end of the crosscut on level 7 a 
parallel northeasterly seam, with crushed fluorite, was cut. Fifty feet south of the 
shaft on level 7 another northeasterly vein was cut, dipping 50° SE.; this is said to 
contain some lead. It shows a streaky mass 1 foot wide mingled with clay and limon- 
ite, but consisting chiefly of celestite or sulphate of strontium, in part crystallized. 

The pay shoot on the Ironclad vein dips southwest on the plane of the vein 
at an angle of about 70°. Its greatest horizontal length is 75 feet. The shoot is 
continuous from level 3 almost down to level 7, but on the latter contains only 
low-grade ore. A fair amount of low-grade ore is claimed to exist on levels 5, 6, 
and 7 outside of the richer pay shoot. 

A thick, well-defined quartz vein, with northeast trend, and containing much 
smoky comb quartz, is encountered between the surface pits on the Magna Charta 
claim and the Ironclad shaft; it has been traced for several hundred feet up toward 
the summit of Ironclad Hill. This same vein is cut by a tunnel from the Magna 
Charta claim, and by a crosscut from a shaft 150 feet deep on the same property. 
It is said to contain only low-grade ore. 

The shaft just mentioned enters hard pyritic breccia a short distance below 
the surface and evidently marks the southeasterly limit of that area of very deep 
oxidation which characterizes Ironclad and Globe hills. The oxidized ore milled 
in the cyanide works of the Homestake Mining Company has thus far been extracted 
from the surface between this shaft and the prominent vein mentioned in the pre¬ 
ceding paragraph. It is reported to average $4 to $5. The South Park shaft was 
sunk in breccia near the Ironclad some years ago to a depth of nearly a thousand 
feet. Little exploratory work was done and it is stated that nothing of value was 
found. 

HOOSIER MINE. 

The Iloosier mine is situated just north of Hoosier Pass and about half a mile 
north of Globe Hill. It is the property of the Grafton Gold Mining Company. 
The total production of the mine is estimated at $360,000. Dividends have been 
paid from the royalties received from lessees. The workings consist of an incline 
shaft 300 feet deep and a vertical shaft about 600 feet deep, in which sinking is in 
progress. The drifts and crosscuts probably aggregate 2,000 feet in length. The 
elevation of the shaft collar is about 10,335 feet. 


MINES AT HEAD OF SQUAW GULCH. 


The vertical shaft begins in breccia about 250 feet south of the granite contact. 
Nothing but breccia is disclosed in the mine workings, and the granite-breccia con¬ 
tact must therefore be steep. The breccia is in general rather fine grained and 
contains much pyrite. 

Three veins are encountered in the mine. On the Discovery, or Hoosier, vein 
the incline shaft was sunk. The vein has a northwesterly strike and dips 65° to 
80° NE. The second vein, called the Ore vein, strikes about 15° more to the north, 
and is nearly vertical. The third is a flat vein, dipping slightly to the south, and 
crosses both the others at a depth of about 250 feet. 

Good ore occurred along the Ore vein, but near the intersection with the 
Hoosier vein the grade was lower; rich ore was, however, found below this inter¬ 
section. The Ore vein is a sheeted zone in breccia, much oxidized toward the top, 
and carries streaks of quartz and kaolin. The upper part of the vein contained 
oxidized ore with free gold. The values are said to have been largely in the kaolin. 
Below the 200-foot level oxidation was slight and fluorite with tellurides made 
their appearance. A 1-inch seam of manganese oxide, probably psilomelane, is 
seen in the vein on level 5 of the vertical shaft. The values of the ore mined 
averaged about S60. 

A shoot pitching to the southeast and averaging 70 feet in horizontal length 
extended from near the surface down to about 350 feet on the Ore vein. Two 
hundred and fifty feet below the surface, at the intersection with the flat vein, the 
width of the pay shoot was reduced from 14 feet above it to 6 inches below it, and 
though the vein was stoped for another hundred feet down, the values were not 
good. It is estimated that 6,000 tons of ore were taken from this stope. A small 
pocket of ore was mined on level 6, 100 feet southeast of the vertical shaft. 

A short distance northwest of the Hoosier is the Friday shaft, sunk 150 feet 
deep between the two veins mentioned above. From a lower shaft on the Friday, 
200 feet deep, some ore is said to have been extracted along a dike. 

HEAD OF SQUAW GULCH. 

Squaw Gulch heads in an amphitheater surrounded by Raven, Bull. Ironclad, 
Globe, and Gold hills. There is here a large area of breccia which has thus far 
proved notably unproductive, though surrounded by mines of demonstrated value. 
No work is being done in this area at present, but the surface bears evidence of 
having been prospected pretty thoroughly. 

The Humboldt, at the end of the southwestern spur from Ironclad Hill, found 
no ore of consequence in its 500-foot shaft. A little of the surface slide rock, how¬ 
ever, was shipped. A vein containing much celestite is reported to course in a 
northeasterly direction from the Humboldt toward the Josie S. shaft, and to con¬ 
tinue over to the Bull Hill side. 

Some ore was taken from a shaft on the east end of the Colorado Boss claim 
on Gold Hill, across the gulch from the Humboldt, but the character of the vein 
could not be determined from examining the dump. 

A dump on the Last Chance claim, just north of the Colorado Boss, shows 
fissures in oxidized breccia with drusy quartz. It is said that no ore was found. 


288 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


The Jeff Davis mine, near Fairview, on the High Line, has several veins, the 
most important being a northwest-southeast vein dipping about 60° NE. The ore 
was oxidized. The production is said to have been between $10,000 and $15,000. 

NORTH SLOPE OF IRONCLAD IIILL. 

Breccia occupies the upper part of the north slope of Ironclad Hill. The lower 
part shows schist and granite in two well-defined areas. Near the contact of schist 
and breccia are several small mines, which, however, have in the aggregate a fairly 
large production to their credit. 

JERRY JOHNSON MINE. 

The Jerry Johnson Mining Company owns the larger parts of the Jerry John¬ 
son claims Nos. 1 and 2, as well as the Arapahoe and Little Pedro claims. The 
output to 1904 is about $125,000. The developments consist of the Jackson shaft, 
450 feet deep; also two smaller shafts and about 1,000 feet of drifts and crosscuts. 
The elevation of the collar of the Jackson shaft is about 10,350 feet. The country 
rock is almost exclusively breccia, the workings approaching the schist contact in 
only one place. 

The two principal veins are the Jerry Johnson, striking about N. 20° W. and 
dipping 45° WSW., and the W. P. H. vein, which first courses almost due north 
and then changes to north-northwest, with a dip of 50° W. Both veins are oxi¬ 
dized throughout and appear as narrow seams of clay or drusy quartz with silicifi- 
cation extending for several inches on each side of the vein. In some places there 
are a few more narrow parallel seams, making the width of the vein range up to 4 
feet. The ore contains very little fluorite. 

On the Jerry Johnson vein little of value was found from the surface down to 
the 300-foot level, but along this level ore occurred from the crosscut north for a 
distance of 80 feet. The ore extended only 40 or 50 feet above the level and was 
taken out about 1 foot wide. At the end of the drift a steep cross seam is faulted 
2 feet by the vein, and a small bunch of ore occurred in the intersection. The 
same cross seam is faulted by the W. P. H. vein. No ore has been developed on 
the 350-foot level. 

The W. P. II. vein lies 100 feet to the northeast of the Jerry Johnson vein. 
Developments on the 300-foot level have shown good values, the shoot extending 
for 100 feet, practically up to the ground of the W. P. II. mine. The central clay 
seam is rich and the rock is taken out 4 feet wide for the screenings. The ore 
reaches 40 or 50 feet above the level to a series of flat seams which are apt to cut 
out the values. In the southern part of the shoot, in what was known as Vogel- 
man’s ground, these flat seams, however, carried values themselves in the foot of 
the vein. At the 400-foot level good values occur at intervals, but it is believed 
that the principal shoot pitches north on the vein and has not yet been reached. 
.This is just below the place where a rich pocket was found in 1904 in the W. P. H. 
mine. 

w. P. H. MINE. 

The property known as the W. P. II. mine, belonging to the Woods Investment 
Company, was in 1904 leased to Harrison & Sevier. The shaft is situated 300 feet 


MINES ON NORTH SLOPE OF IRONCLAD HILL. 


289 


northeast of the Jackson shaft. Some ore was mined in 1903 from the so-called 
contact vein, but in the early part of 1904 a very rich shoot was found in the 
W. P. H. vein, from which during that year a total amount of 8315,000 is reported 
to have been produced. 

The shaft was 245 feet deep when visited, with about 200 feet of drifts on that 
level, corresponding to the 300-foot level in the Jerry Johnson. It is sunk in 
schist, and a short crosscut leads to the contact with the breccia, which dips 40° 
WSW. Some good ore is found on this important contact vein, which continues 
south-southeast to the Damon mine. Both free gold and tellurides occurred, the 
latter in places being contained in fresh schistose rock, in which they have evidently 
formed by replacement. Values are said to be cut off by a flat vein 12 feet below 
the level. The crosscut then continues west for 75 feet, and near the W. P. II. 
strikes a flat vein dipping 20° N., which contains no values, but faults the W. P. H. 
about 6 feet. The latter is twisted, but soon regains its old strike. Irregular values 
began near the flat vein, but gave out. Thirty feet south, on the W. P. IT. vein, a 
small seam with free gold was noted in the hanging wall and immediately led 
into a rich pocket about 20 feet long, 8 feet thick, and extending for 18 feet along 
the dip of the vein above and below the level. It is believed to form part of a nar¬ 
row shoot with northerly pitch. Above the level the values are probably cut off 
by a flat seam, as happened in the Jerry Johnson mine. Many tons of the ore from 
this pocket yielded at the rate of from $1,000 to $6,000 per ton. 

The ore consists of massive and in places silicified breccia ; it contains no fluo¬ 
rite and few large quartz seams. In the main it is oxidized, but tellurides are 
sometimes found, as well as a little galena and zinc blende, but no copper minerals. 
The tellurides in some instances occur directly in fragments of schist and granite 
and have then undoubtedly been formed by direct replacement. The rare minerals 
emmonsite and tellurite, the former a hydrated tellurite of iron, the latter tellu¬ 
rium dioxide, occurred in this rich mass. The ore is very poor in silver, even the 
richest parts rarely containing more than a few ounces to the ton. 

DAMON MINE. 

The Damon mine, which belongs to the Woods Investment Company, com¬ 
prises claims situated a few hundred feet southeast of the Jerry Johnson mine. 
The total production is stated to be over $200,000. Lessees took out $145,000 
between December, 1898, and May, 1901. The developments consist of the Jerry 
Johnson incline, the Damon incline, 270 feet deep, and the Damon vertical shaft, 
500 feet deep. The latter is situated 150 feet northwest of the Damon incline. 
Drifts and crosscuts amount to 3,000 or 4,000 feet. 

The principal country rock is a dense phonolitic breccia. The contact with 
the schist is frequently reached in the workings, but the latter do not extend into 
the schist. 

There are two fairly persistent veins; one of them follows the breccia-schist 
contact, while the other lies parallel to this contact, from 10 to 25 feet to the west 
of it. Besides these two there are a large number of flat veins with dips of from 
10° to 50° in various directions, and which really carried the larger part of the ore. 


290 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

The contact vein is evidently the same which is exposed in the W. P. H. mine, 500 
feet farther north, and at one point in the Jerry Johnson. It contains ore in places, 
but is not uniformly and persistently mineralized. The Damon vein has been 
traced more or less continuously for 400 feet, but is not always distinct. Both veins 
are really narrow sheeted zones, generally oxidized, and sometimes considerably 
shattered. The ores are chiefly contained in the narrow fissures and the oxidized 
tellurides are associated with a little quartz and fluorite. 

The principal ore developments occurred on the upper three levels. Very little 
ore has been taken out from the two lower levels. The Damon incline is sunk 40 
feet vertically in breccia; it then strikes the schist contact and follows its steep 
westerly dip for the remainder of the distance. The principal stopes on the contact 
vein begin near the point where the contact is reached and continue down below 
level 2; in places they are 20 feet wide. Another large stope has been mined on 
the same vein at the Jerry Johnson incline; it is 40 feet long and reaches 40 feet 
above and 10 feet below the level; the width is from 10 to 50 feet, the greatest width 
being attained just above level 2. The stopes on the Damon vein occur chiefly 
where the flat veins join it. One on level 1, at the junction with the principal flat 
vein, is 8 to 10 feet wide. The most important of these flat veins is that met just 
south of the incline on level 1, 60 feet below the collar of the vertical shaft. This 
flat starts at the Damon vein and dips 10° WSW. It has been stoped 6 feet high 
for over 100 feet westward, and the stopes extend north and south for about 200 
feet. It contains one principal and several smaller oxidized seams in very hard 
breccia. It is said that the whole thickness of this vein was ore and some streaks 
6 inches in width averaged 5 ounces per ton. Just south of the incline and a little 
below level 1 a vein is found which dips about 40° NNW. It is stoped 7 feet high, 
the stope trending northward for about 50 feet and making a considerable body 
where it joins the Damon vein. This stope extends down almost to level 2. 

At the west side of the stope, on the contact vein near the Jerry Johnson incline, 
is the top of a raise which leads down into a stope on a vein dipping 45° NNW. This 
stope extends 30 to 40 .feet below level 3. On level 3 a stope has also been opened 
on a flat vein some 50 feet west of the main shaft. 


CHAPTER II.-MINES OF GOLD HILL. 


GENERAL INTRODUCTION. 

Gold Hill lies in the northwestern part of the productive area. Its northwestern 
slope (PI. XXII, A), dotted with mines and with piles of waste rock and crowned 
by the conspicuous shaft house of the Anchoria-Leland mine, forms one of the most 
striking and characteristic views visible from the town of Cripple Creek. The hill 
is composed chiefly of the normal phonolitic breccia, bounded on the north and west 
by the schist and gneiss that underlie the town of Cripple Creek and on the south¬ 
west by the Cripple Creek granite. The breccia is cut by a mass of syenite at the 
southwest contact between the breccia and the granite, and by two masses of latite- 
phonolite, one near Anaconda and one in the upper part of Squaw Gulch, southeast 
of the summit of the lull. 

The principal mines are on the western half of the hill. On the northwest are 
the Anchoria-Leland, Jefferson, Geneva, and Half Moon mines, all in breccia. On 
the west are the Moon-Anchor, Midget, Progress-Gold King, and Conundrum mines, 
partly in breccia and partly in gneiss. On the southwest are the Lexington, E. 
Porter Gold King, Mint, Pointer, Accident, and Red Spruce mines, partly in breccia 
and partly in granite and syenite, while on the south is the Anaconda mine in breccia 
and latite-phonolite. 

Gold Hill is penetrated by a number of long adits. The most northerly is the 
Cripple Creek and Gold Hill tunnel, which is about five-eighths of a mile in length. 
It extends from the town of Cripple Creek in an east-southeast direction and at an 
elevation of about 9,500 feet to the Anchoria-Leland shaft. The Good Will tunnel, 
with its portal 32 feet lower and three-eighths of a mile south of the Cripple Creek 
and Gold Hill tunnel, has a general east-northeast course and also connects with the 
Anchoria-Leland shaft. The Ophelia tunnel, at an elevation of 9,268 feet, enters 
the west base of the hill about three-eighths of a mile southwest of the Good Will 
portal and extends with a nearly east course under the south slope of Gold Hill, 
past Anaconda. This tunnel was over 1J miles in length in 1903, and if carried to 
completion will tap the mines of Bull Hill over 1,000 feet below the surface. The 
Anaconda mine also has a long adit which extends for nearly a mile, in a direction 
slightly east of north, from the town of Anaconda under and past the summit of 
Gold Hill. The portal of this adit is at an elevation of nearly 9,500 feet, or about 
the same as the Cripple Creek and Gold Hill tunnel. 

ANCHORIA-LELAND, JEFFERSON, GENEVA, AND HALF MOON MINES. 

INTRODUCTION. 

The Anchoria-Leland mine, situated on the northwest side of Gold Hill, is 
owned by the Anchoria-Leland Mining and Milling Company, of Denver, incor¬ 
porated in 1892, with a capital of $600,000. The company owns the Anchor, 
Anchor No. 2, Midland, Lillian Leland, Chance, City View, and Cottontail claims, 


291 


292 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

and also the Conundrum claim, which is elsewhere described. The mine has been 
worked principally by lessees and made its first shipment in 1895. It continued 
productive until the latter part of 1899; since then but little ore has been shipped. 
The Jefferson mine lies just north of the Anchoria-Leland, with workings confined 
to the Mattie L. claims. It is owned by the Jefferson Mining Company, of Denver, 
incorporated in 1892, with a capital of $1,100,000. The Geneva mine is northeast 
of the Jefferson and belongs to the Stratton estate, having been purchased in 1900, 
with the May Queen claim, for $300,000. Neither the Jefferson nor the Geneva 
mine is at present actively worked. The Half Moon mine is situated south of the 
Geneva and east of the Anchoria-Leland. It is owned by the Matoa Gold Mining 
Company, of Colorado Springs, incorporated in 1892, with a capital of $1,000,000. 
The company owns the Half Moon, Harlan H., and Gold Pass No. 1 claims, with 
other property in Arequa Gulch. Ore was discovered in the Half Moon in 1893 at a 
depth of 250 feet, and shipments were made at intervals for about five years. 

PRODUCTION AND DIVIDENDS. 

The Anchoria-Leland is credited with a gross production of over $1,000,000, 
and has paid $198,000 in dividends. The first dividend, $6,000, was declared in 
1896 and the last, $18,000, in 1899. The gross production of the Jefferson is not 
accurately known, but is probably between $300,000 and $400,000. The Geneva 
shipped considerable ore in 1895, 1896, and 1897, but the gross production has not 
been ascertained. The Half Moon mine has produced between $600,000 and 
$700,000, chiefly through lessees. One dividend, $25,000, was declared in December, 
1898. 

UNDERGROUND DEVELOPMENT. 

The principal workings of this group of mines are on the Anchoria-Leland 
property. The Anchoria-Leland shaft is 1,100 feet deep, the collar being 10,139.46 
feet above sea level. The first main level is 277 feet below the collar. Level 2 is 
65 feet below level 1; level 4 is 153 feet below level 2; the Cripple Creek and Gold 
Hill tunnel is 270 feet below level 4; the Good Will tunnel, or level 6, is 32 feet 
lower; and level 8 is 142 feet below the Good Will tunnel. Levels 9, 10, and 11 
follow at intervals of 96 feet. The levels of chief importance from their extent, 
productiveness, or geological interest are 1, 2, 4, and the two adit levels. The 
principal drifts are on the Chance lode and run nearly north-northeast and south 
and southwest. (See fig. 25.) The Jefferson and Geneva drifts are on the same 
line of Assuring. About 300 feet southeast of the Chance drifts is a series of drifts 
with nearly the same trend, on the Matoa and Potter lodes. Northwest of the 
Anchoria-Leland shaft there has been some irregular and disconnected drifting 
along the City View lode, which is associated with a basaltic dike. These drifts 
are mostly from 200 to 250 feet northwest of the Chance drifts and approximately 
parallel to the latter. There is a fourth series of drifts running north-northwest 
and south-southeast on the Mahoney lode. The Jefferson incline, 450 feet north¬ 
east of the Anchoria-Leland shaft, is about 650 feet deep and has eight short levels. 


U. S. GEOLOGICAL SURVEY 


PROFESSIONAL PAPER NO- 54 PL. XXII 



A. NORTH SLOPE OF GOLD HILL. 
Anchoria-Leland mine on right; Half Moon mine on left. 



B. WEST SLOPE OF RAVEN HILL. 

Showing Doctor-Jackpot and Morning Glory group of mines. 













MINES OF GOLD HILL. 


293 


The property is dotted with small shafts, most of which were sunk by lessees in 
the early period of the mine's history, when each lessee sunk a shaft on his particular 
section of a lode. 

GEOLOGICAL FEATURES. 


The general country rock of the Anchoria-Leland mine is the usual breccia of 
Gold Hill. This is cut by a few unimportant dikes of phonolite and by the City 
View basic dike. This dike is exposed in the Good Will and Cripple Creek and 



Fig. 25.—Plan of level 1 of Anchoria-Leland mine and of adjacent levels of the Jefferson, Geneva, and Half Moon mines, 

showing principal lodes. 


Gold Hill tunnels, in the old Progress workings on the Gold King claim, in the City 
View workings, and on several of the main Anchoria-Leland levels. On the north¬ 
east it approaches the Chance lode and the two apparently come together near the 
Geneva shaft. The Geneva workings, however, were not visited. Like other 
basic dikes in the district, the City View dike frequently branches and pinches. In 
the Good Will tunnel at least four narrow “basalt” dikes are exposed in a zone 
about 300 feet wide. All may be branches of the City View dike. The dike is 
usually less than 2 feet in width. 










294 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

LODE SYSTEMS. 

The Chance lode passes close to the Anchoria-Leland shaft, with a general 
strike of N. 30° E. The lode is curved, however, the strike in different portions 
ranging from N. 15° E. to northeast. The dip also is variable, ranging from vertical 
southwest of the shaft to 80° in the Jefferson mine. The Chance lode has been 
explored for a length of over 1,200 feet. The Matoa lode is from 300 to 400 feet 
southeast of the Chance, and strikes N. 25° E. It is a complex and irregular lode 
of varying dip. In the Anchoria-Leland ground it meets the Potter lode, which 
strikes N. 55°-65° E. and dips north. In the region of intersection the two lodes 
lose their identity in a plexus of irregular fissures. The Matoa lode has been explored 
to a length of about 500 feet and the Potter lode for nearly 200 feet. About 200 
feet northwest of the Chance lode is the City View lode, which in part coincides 
with the City View “basalt” dike and has a general northeast strike. The iode 
dips north, but exhibits considerable irregularity. The workings on the City View 
are unsystematic, disconnected, and in part inaccessible, so that it was impracti¬ 
cable to verify an impression gained at the time of visit, namely, that the name 
City View had been applied to different fissure zones in different parts of the work¬ 
ings. Between 300 and 400 feet northwest of the City View dike is the Wardel 
lode, which strikes N. 60° E. and dips about 85° NW. The Maloney lode inter¬ 
sects the Chance lode from 100 to 200 feet northeast of the Anchoria-Leland shaft. 
It strikes N. 30° W. and dips 80° NE. from the surface to level 3. Below level 3 it 
either changes its dip or is replaced by a rather indistinct sheeted zone with a north¬ 
westerly dip of 70°. The Maloney lode is not known northwest of the Chance lode. 
A long drift has been run in this direction on level 2, but the fissure followed con¬ 
tains no ore and dips southwest instead of northeast. The Maloney and Potter 
lodes cross withoift any appreciable faulting, the Maloney continuing through the 
Lexington mine into the E. Porter Gold King mine. 

Some of the best-defined and most persistent fissures in these mines contain no 
ore. A good example of this is the so-called Fault vein, which has a curved but 
generally northwest strike and dips from 55° to 70° SW. This crosses the City 
View and Chance lodes near the Jefferson line and the Matoa lode near the Half 
Moon line, continuing south past the Tipton shaft. It slightly displaces the City 
View dike and possibly also the Chance and Matoa lodes. The displacement, how¬ 
ever, probably nowhere exceeds 5 or 6 feet. The Fault vein is a sheeted zone, one 
or more of the fissures usually containing a few inches of soft decomposed or crushed 
breccia. This gouge material contains a little pyrite, but no ore. 

Another barren fissure zone is the Iron vein. This strikes a little west of 
north and dips east. It is exposed on several levels northwest of the Anchoria- 
Leland shaft and crosses the City View lode without perceptible faulting. 

The general relations of these fissures to one another are shown in fig. 25. 

CHARACTER OF ORE. 

All of the ore from these mines has come from the zone of complete or partial 
oxidation. No ore was visible at the time of visit. It appears to have consisted 
originally of calaverite, with quartz and fluorite, and to have been largely altered 
to free gold. 


MINES OF GOLD HILL. 


295 


PAY SHOOTS AND LODE STRUCTURE. 

All of the ore in the Anchoria-Leland mine except that in the City View dike 
occurred in typical narrow sheeted zones in breccia. The maximum width of the 
ore appears to have been about 5 feet. In places the sheeted structure is remarkably 
well developed, the rock having been fissured for a total width of a foot or more into 
thin plates a fraction of an inch in thickness. On each side such close sheeting 
passes through more widely spaced Assuring into the ordinary country rock. Such 
highly developed sheeting may be seen in the Chance and Wardel lodes on level 4, 
and less conspicuously in the Matoa lode. The fissures are often fdled or partly 
filled with quartz or quartz and fluorite. In spite of the great regularity exhibited 



Scale , 

o ioo zoo 3ooteet 


Fig. 26 .—Longitudinal section of the Chance vein, Anchoria-Leland mine, showing vertical range of ore. 

for short distances by these sheeted zones, they are not as a whole notably persistent. 
They sometimes dwindle to a single indistinct fissure or come to an end upon 
meeting another fissure zone of somewhat different strike and dip. This is well 
illustrated by that part of the Matoa lode within the Anchoria-Leland ground. The 
ore in this lode, as shown in the abandoned stopes, changed repeatedly from one set 
of fissures to another set of divergent dip or strike. 

The most striking fact in connection with the Anchoria-Leland mine is the 
comparatively slight depth to which the ores extended. The Chance lode has, so far 
as known, no ore below level 2, and very little ore below level 1. Practically all the 
ore, in other words, was within 300 feet of the surface. Furthermore, the five or six 









































296 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

lessees’ shafts on the Chance lode all passed through a barren zone, extending from 
75 to 100 feet below the surface, before they reached the top of the ore (fig. 26). 
The Maloney lode exhibits a similar barren zone near the surface, and contains no 



ore below level 2 in the Anchoria-Leland mine (fig. 27). In the Lexington mine, 
however, just south of the Anchoria-Leland, the ore is said to have extended to 
greater depth. 










































































































MINES OF GOLD HILL. 


297 


The pay shoot of the Chance lode extended from a point 100 feet southeast of 
the Anchoria-Leland shaft to a little beyond the Jefferson shaft—a length of about 
600 feet. Details of the occurrence of the ore in the Geneva mine were not obtained, 

i • • * . 7 

but it appears from the mine maps to have occurred near the intersection of the com¬ 
bined Chance lode and City View basalt dike with some cross fissures of north to 
northwest strikes. 

In the Matoa lode the largest and most continuous ore body occurred in the 
Half Moon ground, northeast of the fault vein. Southwest of the fault vein the 
Matoa lode becomes a complex of intersecting fissures and the ore occurred in more 
or less isolated bunches. 

In the Maloney lode the pay shoot extended from the Chance lode into the 
Lexington ground, pitching south at a low angle. Near the Chance lode the bot¬ 
tom of the Maloney ore was about 25 feet above level 1 of the Anchoria-Leland. 
Near the Lexington line, 300 feet farther south, the ore stopped about the same 
distance above level 2. The Lexington mine was not visited, but the main Maloney 
ore shoot apparently did not extend for more than 100 feet beyond the intersection 
with the Potter lode. 

The City View lode is a sheeted zone in breccia which in some places follows the 
City View dike. It contained some ore near the surface, both in the breccia and in 
the dike. The Wardel lode also contained some small bodies of ore between the 
surface and level 4 of the Anchoria-Leland. It is a narrow sheeted zone in breccia. 
The rock is sometimes divided by this sheeting into very thin plates for a width of 5 
or 6 inches, with more widely spaced fissures on each side. Locally the medial part 
of the lode may pass from thinly sheeted to brecciated material. 

UNDERGROUND WATER. 

The first water encountered in the Anchoria-Leland shaft was 653 feet below 
the collar, or 9,486 feet above sea. As the Moon-Anchor mine, however, had been 
pumping for some time ere the Anchoria-Leland reached water, the above level was 
probably below the natural water level. The maximum flow (550 gallons per 
minute) was reached 97 feet below the level of first water. The bottom of the shaft, 
9,029 feet above sea, is now dry. 

MOON-ANCHOR, MIDGET, AND CONUNDRUM MINES. 

INTRODUCTION. 

These three mines, while under separate ownership and management, are 
so closely connected as best to be described together. They are situated on the west 
slope of Gold Hill in the vicinity of the contact between the breccia and the gneiss. 
The Moon-Anchor mine is owned by the Moon-Anchor Consolidated Gold Mines 
(Limited), of London, capitalized at £2,000,000, and comprises the Little Anna 
Rooney, New Moon, and parts of the Anchor and Anchor No. 2 claims. The prop¬ 
erty was originally owned by the Moon-Anchor Gold Mining Company and was sold 
to the English corporation in 1899. Ore was first shipped from the Anchor claim in 
the latter part of 1895, and from the New Moon in 1896. In the latter year the two 
mines, hitherto worked by lessees, were combined as the Moon-Anchor, the new 


298 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


company declaring its first dividend in the summer of 1897, and continuing to ship 
ore up to the transfer of the mine to its present owners. 

The Midget mine, comprising the Protection, Maryland, Sunnyside, Midget, 
Cumberland, and parts of several other claims, lies southwest of the Moon-Anchor 
and is owned by the Midget Gold Mining and Milling Company, of Colorado Springs, 
capitalized at 81,000,000. The company also holds a lease on a part of the Bonanza 
King claim. 

The Conundrum mine, owned by the Anchoria-Leland Mining and Milling Com¬ 
pany, lies immediately northwest of the Moon-Anchor and Midget mines. Prior to 
1900 a little prospecting only had been done on the Conundrum claim. During the 
last three years, however, it has been developed into a productive mine. 

PRODUCTION. 

Prior to its sale to the present owners the Moon-Anchor mine produced consid¬ 
erable good ore and paid dividends amounting to 8261,000. Of late years it has 
not been so productive and has been worked chiefly by lessees. 

The gross production of the Midget mine, as furnished by the company, is as 
follows: 

Production of Midget mine, 1900-1904. 


1900 . $318,973.65 

1901 ... 121,710.01 

1902 . 77,269.85 

1903 . . 143, 9S9. 84 

1904 . 96, 932. 34 


758,875.69 

The mine also produced a little ore in 1895, before the incorporation of the 
present company. 

UNDERGROUND DEVELOPMENT. 

The Moon-Anchor shaft was a little over 870 feet deep at the time of visit. 
Sinking had been begun by the company in December, 1903, the shaft at that time 
being about 835 feet deep. On January 9, 1904, water was encountered 870 feet 
below the collar, and work was stopped. This water, however, subsequently disap¬ 
peared, and sinking was resumed near the end of the same month. The upper level, 
known as level 4, is 422 feet below the collar, which is 9,864.73 feet above sea 
level. Below this are levels 5, 6, 7, 8, and 9 at intervals of 104, 103, 65, 47, and 59 
feet, respectively. The principal drifts run nearly northeast-southwest. 

The Midget shaft, 550 feet southwest of the Moon-Anchor, has its collar 9,796.2 
feet above sea level, and at the time of visit was about 800 feet deep. There are 
ten main levels. Level 5 is about 300 feet below the collar. Below 5 the levels are at 
approximately 100-foot intervals, except levels 9 and 10, which are 60 feet apart. 
The main drifts in the Midget fall into three classes—a series of drifts running in 
general north-northeast and south-southwest on the Midget lode, a series running 
east-northeast and west-northwest on the Bonanza King lode, and a series of nearly 
north-south drifts on the Conundrum lode. These drifts in general converge in the 
vicinity of the gneiss and breccia contact southwest of the Midget shaft. 








MINES OF GOLD HILL 


299 


The Conundrum mine is worked through an adit, at the end of which is an under¬ 
ground station and an inclined winze on the lode. Hoisting is done by electric power. 
Although the top of the station, excavated in gneiss, is only about 50 feet below the 
surface of the hill, no timbering is necessary and the station is practically dry. The 
adit enters Gold Hill 450 feet west of the Midget shaft and about 130 feet below the 
collar of the latter and runs for 300 feet N. 20° E. until it reaches the lode. The 
winze goes down on the dip of the lode, about 70° E., to a vertical depth of 620 feet 



Fig. 28.—Geological plan of portion of level 3 of the Conundrum, level 7 of the Midget, and level 6 of the Moon-Anchor mine, 

showing relations of principal lodes. 


below the adit. There are six main levels, the successive vertical intervals from the 
adit down being 110, 155, 135, 60, 95, and 65 feet. The workings of the Conundrum 
are simple and consist chiefly of drifts along the nearly north-south lode. There 
is, however, an important stope in the northern part of the mine on a zone of cross- 
fissuring. 

A general understanding of the relation of the workings of these three mines 
may be had from figs. 28 and 29. 










300 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


GEOLOGICAL FEATURES. 

The Moon-Anchor workings are entirely within the breccia, the Midget workings 
are partly in breccia and partly in the fine-grained gray gneiss of this vicinity, and the 

Conundrum workings, which 
for the most part follow the 
Conundrum basic dike, are 
chiefly in gneiss. 

The contact between the 
gneiss and breccia is irregular, 
is often very poorly defined, 
and lias not been exposed in a 
sufficient number of places to 
fully establish its form and 
character. Near the Conun¬ 
drum incline the contact at 
the surface practically coin¬ 
cides with the Conundrum 
dike. It dips, however, at a 
somewhat lower angle to the 
east than does the dike, and 
on the lower levels of the Co¬ 
nundrum mine lies within the 
little-explored hanging wall of 
the lode. Thus on level 8 of 
the Midget, northeast of the 
shaft, the contact is about 35 
feet east of the Conundrum 
dike. On level 9 the Midget 
shaft is in gneiss, showing the 
contact to be here at least 90 
feet east of the dike, and indi¬ 
cating a decided local flatten¬ 
ing of the dip. North of the 
Conundrum incline the breccia 
seems to overlie the gneiss in 
such a manner as to indicate 
an unusually low inclination 
of the contact. This is shown 
by a northeast crosscut from 
level 6, which extends to a 
point 1,050 feet northeast of 
the portal of the Conundrum 
adit or 400 feet north-north¬ 
west of the Moon-Anchor 
shaft. This crosscut is all in gneiss, although a vertical line through its face would 
emerge at the surface in the breccia fully 700 feet from the nearest exposure of gneiss. 



Fig. 29.—Diagram showing relative position of levels in Conundrum and 

Midget mines. 











































































MINES OF GOLD HILL. 


301 


(See PL II, in pocket.) The southeasterly dip of the contact, near the bend in the 
latter between the Conundrum and Abe Lincoln mines, is thus probably rather under 
40°. In both the Midget and Conundrum mines the gneiss, sometimes for a hundred 
feet or more from the volcanic breccia, is shattered to fragments, which often average 
only 2 or 3 inches in diameter. This shattering is very noticeable along both sides of 
the Conundrum lode, and it is usually impossible to determine closely where the shat¬ 
tered gneiss ends and the volcanic breccia begins. The fragments of gneiss are partly 
separated by interstices as if the liner material had been in part removed. The frag¬ 
ments are in some cases only slightly coherent; in others they are coated and cemented 
by crystalline envelopes of purple flfiorite. The shattering evidently antedated the 
intrusion of the basaltic dike, as the latter is not brecciated. 

The breccia in the Midget and Moon-Anchor mines is more varied in texture and 
composition than is common in so small an area. It usually contains abundant frag¬ 
ments of phonolite, schist, granite, and gneiss held together in a matrix containing 
many minute particles of pink feldspar, evidently derived from the granite and gneiss 
of the vicinity. This variety of the breccia may be well seen in the dump of the Ben 
Hur shaft, south of the Midget. Another variety occurs along the general line of the 
Midget lode, particularly between level 6 and the surface, where it may be seen in 
various pits between the Moon-Anchor and Midget shafts. This is a line-grained 
altered tuff, which underground somewhat resembles decomposed basalt, and is 
characterized by a reddish or purplish tint. The clastic structure of this material is 
sometimes plain, sometimes obscure, and in the latter case the rock is often called 
basalt by the miners. 

The breccia in the'Midget and Moon-Anchor mines has undergone local shat¬ 
tering similar to that already described in the gneiss near the Conundrum lode. In 
the Midget this shattered rock occurs in the vicinity of the shaft on levels 7 and 8, 
passing into brecciated gneiss on levels 9 and 10. The rock is a loosely coherent, 
porous mass of angular fragments, showing considerable pyrit.ic mineralization. 

' No ore occurs in this material, and lodes as they enter it from the solid breccia are 
lost. Similar shattered breccia occurs on levels 7, 8, and 9 of the Moon-Anchor 
mine just northwest of the shaft, the material looking as if it had been passed 
through a rock crusher and dumped into an old stope. The fragments are in part 
loose, in part cemented at points of contact by pyrite and quartz. This material 
passes peripherally into breccia traversed by countless fractures belonging to 
sheeted zones running in various directions through the rock. This fissured rock in 
turn passes gradually into breccia showing only the usual amount of jointing. 

Both gneiss and breccia are cut by several irregular dikes of phonolite, which 
are also locally shattered, though usually less so than the breccia. These dikes 
are often indistinct and difficult to trace in the breccia, particularly in the shat¬ 
tered portions. 

The Conundrum basalt dike strikes on the whole a little west of north and dips 
about 70° E. It is rather curved and irregular and ranges in width from a frac¬ 
tion of an inch up to 3 feet. It is usually mineralized, constituting ore, or is soft 
and decomposed. 

13001—No. 54—06-21 



302 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


LODE SYSTEMS. 

The Conundrum lode is coincident with the Conundrum “basalt” dike and has 
a general strike of N. 5° W., with an easterly dip of 70°. The Bonanza King is a 
strong, regular lode which lies south of the Midget shaft and strikes N. 60° E. It 
dips steeply to the northwest. The Midget lode, near the Midget shaft, strikes N. 
23° E. As the Moon-Anchor mine is approached, however, the lode curves east¬ 
ward, and near the compromise line between the two properties strikes N. 50° E. 
South of the shaft the Midget lode curves gently southward and crosses the Bonanza 
King lode with a nearly north-south strike. # That part of the lode south of the 
Bonanza King is known as the Murray lode. The Midget lode dips southeasterly, 
the angle ranging from 60° south of the Bonanza King to nearly 80° near the Moon- 
Anchor ground. The Midget and Bonanza King lodes cross without any apparent 
faulting or any indication of difference in age. The Conundrum lode usually 
becomes irregular and rather indistinct as it approaches the Bonanza King lode. 
The two apparently cross without noticeable faulting, but the Conundrum lode has 
proved of very little economic importance near the Bonanza King. About 100 
feet northwest of the Midget shaft is a lode known as the Intermediate vein, w T hich 
accompanies a phonolite dike. This strikes in general N. 60° E., it and the Midget 
lode coming together near the Moon-Anchor ground. What becomes of the Midget 
lode in the Moon-Anchor mine is not clear. The principal lode of that mine, the 
Cobb vein, is associated with a phonolite dike and is apparently a direct continua¬ 
tion of the Intermediate lode of the Midget mine. The Intermediate or Cobb lode 
dips steeply northwest. The Cobb lode in the Moon-Anchor is accompanied by a 
number of other fissures in the breccia, which show a general tendency to diverge 
to the northeast. It is crossed at an acute angle by the Lead vein, which, so far as 
knowm, has not been recognized in the Midget workings, though it may be the 
Midget vein. The general strike of the Lead vein is N. 30° E., and the dip about 
70° SE. The intersection of these lodes is w r ell shown on levels 7 and 8 of the Moon- 
Anchor mine. The Lead vein, as it comes into the Cobb from the south, turns and 
follows the latter for 75 to 100 feet and then resumes its former course and contin¬ 
ues into the hanging wall of the Cobb lode. The phonolite dike, which elsewhere 
invariably accompanies the Cobb, is absent where the tw r o lodes coincide, being 
apparently faulted by the Lead fissure. 

The so-called Granite vein in the Moon-Anchor mine strikes nearly northwest 
and southeast. It is a nearly vertical, narrow zone in the breccia characterized 
by unusual abundance of granitic fragments. It was apparently a fissure in at 
least partly consolidated breccia, which became filled largely with granitic detritus. 
This filling has been mineralized with pvrite, and most of the granitic fragments 
are altered to spongy aggregates of secondary feldspar. 

CHARACTER OF ORE. 

Not. much ore could be seen in the Moon-Anchor mine at the time of visit. 
It appears to have been of the usual type—calaverite and fluorite in narrow fissures 
in breccia and phonolite—and w r as partly or w holly oxidized above levei 6. Some 
of the best ore is said to have occurred in the phonolite dike of the Cobb lode. 




MfNHS OF GOLD HILL. 


303 


In the Midget mine the ore in the Midget lode nearly all occurs above level 6 
and is all partly oxidized. Calaverite, free gold, and fluorite are said to be charac¬ 
teristic constituents. As seen just above level 6, this ore consists of breccia con¬ 
taining small disseminated crystals of pvrite and traversed by minute irregular 
veinlets of fluorite. Some of the veinlets are oxidized and show a little rusty gold. 
No calaverite was seen, but it is said to be sometimes visible. The ore of that nart 
of the Bonanza King lode which is in breccia is similar to the ore of the Midget 
lode. In the gneiss, however, the ore is distinguished from the country rock by 
the presence of tiny veinlets of pyrite. These veinlets sometimes contain a little 
quartz, feldspar, and fluorite, but so far as observed no visible calaverite. That 
calaverite or sylvanite is really present with the pyrite in the little veinlets is clearly 
shown, however, by the action of oxidation, which within 30 or 40 feet of the sur¬ 
face has changed the telluride to visible specks of dull native gold, while the pyrite 
is unaltered. 

The ore of the Conundrum lode consists of mineralized “basalt.” The rock 
is traversed by numerous narrow fissures, sometimes reticulating, but usually 
showing general parallelism with the dike walls. These little fissures are filled or 
partly filled, sometimes with purple fluorite, sometimes with quartz, and some¬ 
times with both minerals together, giving the rock a handed appearance. These 
gangue minerals are not always confined to the fissures, but sometimes permeate 
the altered basalt between the distinct fractures. 

As seen under the microscope, the “basalt” between the veinlets is thickly 
sprinkled with minute pyritohedral crystals of pyrite and with granules of sec¬ 
ondary quartz. These lie in an exceedingly fine-grained and obscurely crystalline 
aggregate of uncertain composition. It appears to be partly quartz, partly feld¬ 
spar, and partly some isotropic material, but the texture of the material is too 
fine for the microscopical determination of its constituents. It reveals no trace of 
the original igneous texture of the rock. 

The gold occurs as calaverite associated with the quartz and fluorite and with 
pyrite. The ore, however, is often oxidized even below level 9 of the Midget or 
level 5 of the Conundrum, and the calaverite changed to native gold. Little 
specks of galena and sphalerite are common in the Conundrum dike, usually accom¬ 
panying the gold ore. These minerals appear to have been deposited at least in 
part by replacement of the basalt and sometimes form bunches or lenses several 
feet long and 5 or 6 inches in thickness. This galena and sphalerite ore frequently 
contains 2 or 3 ounces of gold and about the same quantity of silver per ton. Galena 
and sphalerite are not confined to the Conundrum lode, but occur also in the Midget 
mine in the Bonanza King lode as lenticular masses a foot or so in thickness, replac¬ 
ing fissured gneiss. On level 8 this galena and sphalerite are associated with the 
usual calaverite gold ore and barely pays to mine. In the Moon-Anchor mine 
galena, sphalerite, and pyrite, associated with quartz, fluorite, and rhodochrosite, 
constitute the Lead vein, in breccia. 

The ore in gneiss in the northern part of level 6 of the Conundrum consists of 
calaverite, often beautifully crystallized, occurring in the vugs of quartz-fluorite 
veinlets. 


304 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


PAY SHOOTS AND LODE STRUCTURE. 

The Cobb, the principal lode in the Moon-Anchor mine, is a zone of Assuring 
along a phonolite dike, the latter being usually less than 2 feet wide. On level 4 
of the Moon-Anchor, which is about 35 feet above level 6 of the Midget, the Cobb 
lode has been sloped for about 200 feet, these stopes being continuous with those 
on the Midget lode. The Midget and Cobb ore bodies are thus in reality parts of 
a single pay shoot, although, as already pointed out, the Cobb phonolite dike, 
accompanied by some Assuring and mineralization, is probably what is known as 
the Intermediate vein in the Midget mine. (See Ag. 28, p. 299.) The Midget- 
Cobb pay shoot pitches northeast at an angle of about 45°. At a depth of about 
400 feet it crosses the provisional or “compromise” line from the Midget into the 
Moon-Anchor ground and at the same time changes from the Midget Assure zone 
with southeasterly dip to the Cobb Assure zone with northwesterly dip. Just 
what takes place at the point of change is difficult to determine in the present state 
of the workings. It is certain that a number of other Assures, including the Lead 
vein, converge toward the debatable ground where the Midget, Cobb, and Inter¬ 
national lodes come together. On the lower levels of the Moon-Anchor the Cobb 
pay shoot is shorter and is usually conAned to the intersection of the Lead and 
Cobb lodes. The ore in such case occurs in the sheeted breccia on one or both 
sides of the sphalerite and galena streak of the Lead vein. The latter, so far as 
known, contains no workable ore. The only ore thus far stoped from the Inter¬ 
mediate lode in the Midget mine occurs just above level 6, northwest of the shaft. 
In the Murray lode, which is the continuation of the Midget lode south of the 
Bonanza King lode, some small pay shoots have been worked just above level 6 of 
the Midget. 

In the Bonanza King lode the ore occurs in two rather irregular pay shoots, 
one mainly in the breccia and one mainly in the gneiss. The ore in the breccia 
lies chieAy to the east of the Midget or Murray lode and has been stoped from the 
surface to level 6. Its maximum length is about 350 feet, but it includes some 
portions of the lode too low in grade to work and might be considered as made up 
of two or more separate pay shoots. 

The western pay shoot, in gneiss, is more compact and irregular. It has been 
stoped from a point above level 5 to level 7, and ore is known also on level 8. This 
pay shoot pitches about 60° SW. and attains its greatest length, 250 feet, near 
level 6. The gneiss along the course of the lode is traversed by numerous small 
irregular Assures which contain the ore. The stopes are occasionally 15 or 20 feet 
wide. In the western part of the workings, near the Protection and Mariposa 
shafts, the Bonanza King lode is crossed by some small Assures striking north- 
northeast. The gneiss in the vicinity of these interstices is traversed by numerous 
small irregular fractures containing pyrite and calaverite, with quartz and Auorite. 
This ore is being stoped between the Midget level 5 and the surface. It forms 
irregular bodies at the intersections of the more prominent Assures and is partly 
oxidized. 

The main pay shoot of the Conundrum lode lies partly in the Midget mine and 
partly in the Conundrum. The pay^ shoot begins near level 1 of the Conundrum 


MINES OF GOLD HILL. 


305 


and becomes longer on successively lower levels, reaching a maximum length of 
about 600 feet on level 9 of the Midget and level 5 of the Conundrum. Below this 
only a few isolated bodies of pay ore have as yet been found. The pitch of the 
southern edge of the ore body is practically 90° and of the northern edge about 45° 
to the north. 

The ore of the Conundrum lode is confined to the “basalt” dike, which is 
usually from 18 inches to 3 feet in width. The dike is traversed by numerous 
little fissures, usually parallel to the walls, but sometimes of irregular trends. 
These range in width from an eighth of an inch to those visible only with a strong 
lens or microscope. The calaverite occurs chiefly in the quartz and fluorite veinlets 
filling these fissures, but probably to some extent throughout the mass of the rock, 
which is altered to a gray porous material containing pyrite in minute crystals 
implanted on the walls of the little cavities and disseminated through the rock. 

In the northern part of the Conundrum mine, in the Mary Ann claim, is an 
important pay shoot in gneiss which has been stoped from level 6 nearly to level 
5, and has been explored by a winze below level 6. The ore occurs in a zone of 
east-west Assuring, just east of the basalt dike. On an intermediate level, 50 feet 
above level 6, this pay shoot was about 70 feet in length and on level 6 about 25 
feet in length. On both these levels the ore was found to be limited on the west 
by the basalt dike and on the east by a phonolite dike striking northeast and dipping 
northwest about 75°. Below level 6 the ore, as followed in the winze, is said to go 
through the phonolite dike and continue into the gneiss on its under side. Although 
the ore body has a general east-west trend it is not a distinct lode, but consists 
of a number of small intersecting fissures of various dips and strikes and has no 
definite walls. The ore occurs in the fissures as calaverite in a quartz and fluorite 
gangue. It is unoxidized. 

O o 

UNDERGROUND "WATER. 

The Moon-Anchor shaft, the first of the three to reach any considerable depth, 
originally encountered water, in April, 1899, 376 feet below the collar, or 9,489 
feet above sea level. The flow was about 400 gallons per minute. The maximum 
flow, however, 1,100 gallons per minute, was found near level 6, or 9,241 feet above 
sea level. This water slowly receded and in January, 1903, the sump, 9,030 feet 
above sea level, was dn r . Early in 1904 water was again encountered 870 feet 
below the collar of the shaft, or 8,994.7 feet above sea level, but this soon disap¬ 
peared, allowing sinking to be resumed without pumping. The water record of 
the Midget shaft presents no additional features of interest, and the Conundrum, 
keeping above the water level, has always been dry. 

E. PORTER GOLD KING MINE. 

The E. Porter Gold King mine is situated a few hundred feet south of the 
summit of Gold Hill. Its production is estimated at $50,000. The underground 
development consists of a shaft about 500 feet deep and four levels representing 
1,500 feet of drifting. An incline called the Jaycox shaft extends from the surface 
to level 1. The entire workings are in breccia. A “basalt” dike with a practi- 
callv north-south course is shown by surface pits and is cut on level 4. 


I 


306 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

Several veins have been opened in the mine. The principal one has a south- 
southeast course and an easterly dip of 75° to 80°. It outcrops west of the main 
shaft and is followed by the Jaycox shaft. This vein has been stoped for 120 
feet, from the surface down to level 2, and has been stoped also in the Lexington 
mine. A vein with similar strike, but nearly vertical, runs through the main 
shaft. It has been stoped a little about 50 feet north of the shaft. A north- 
south vein recently opened on the 150-foot level just east of the shaft is furnishing 
ore. A vein with a north-northeast direction has been cut just north of the shaft 
on level 2, and has furnished some ore. 

MINT, POINTER, ACCIDENT, AND RED SPRUCE MINES. 

INTRODUCTION. 

The Mint, Pointer, Accident, and lied Spruce mines are situated on the south¬ 
west spur of Gold Hill, near the “Low Line” track. They have been intermit¬ 
tently worked, chiefly by lessees, and the greater part of the ore has come from 
the Pointer mine, which began shipping in 1896 and is still producing. The Acci¬ 
dent shipped a little ore in 1897 and again in 1902, but was idle at the time of 
visit, as was the Red Spruce. The Mint shipped ore in 1901, and was being operated 
by lessees early in 1904. All are small mines. 

UNDERGROUND DEVELOPMENT. 

The Pointer shaft is 530 feet deep, with seven levels. The Mint shaft, 600 
feet northeast of the Pointer, is about 750 feet deep and has four levels—levels 
3 and 4 of the Mint being continuous with levels 5 and 7 of the Pointer respec¬ 
tively. The Accident shaft is about 330 feet northwest of the Pointer shaft,the 
two being connected by level 5 of the Pointer. The Red Spruce shaft is close to 
the Accident. Neither of these shafts were entered and no maps of their under¬ 
ground workings were seen. The principal drifts in the Pointer and Mint mines 
run approximately northeast-southwest. 

GEOLOGICAL FEATURES. 

/ 

The geological relations are somewhat obscure, owing to poor surface expo¬ 
sures and limited underground development. The Mint shaft is in breccia, just 
north of the main contact. The Pointer shaft is in a mass of syenite, which is 
described on page 85. This syenite is exposed also in the Ophelia tunnel, south 
of the Pointer shaft, where it exhibits porphvritic facies near the contact with 
the breccia and is apparently irregularly intruded into the latter. The breccia 
near the syenite is altered to a hard, ringing rock which contains disseminated 
pyrite and in which the original clastic structure is partly obliterated. The relation 
of the syenite to the older granite of the vicinity is nowhere clearly shown. The 
syenite, however, is presumably intrusive into the granite. The syenite and 
breccia are cut by some irregular dikes of phonolite and “basalt.” The contact 
between the syenite and breccia is very irregular, and on the lower levels the 




I 


MINES OF GOLD HILL. 807 

intrusive rock extends much farther northeast than it does on the surface. It is 
the prevailing rock in the crosscuts which extend from the Mint shaft under the 
abandoned Keystone shaft, which is 150 feet east of the Mint. 

LODE SYSTEMS. 

The principal lode is the Pointer, which strikes N. 33° E. and dips 80° NW. 
The Pointer and Mint shafts are approximately on the line of the lode. In the 
Pointer workings the lode is very close to the contact between the syenite and 
breccia. It is in syenite down, to level 7, and that level practically marks the 
contact. About halfway between the Pointer and Mint shafts the lode passes 
through a phonolite dike. Northeast of the dike the Pointer lode is in breccia, 
and is less distinct than in the Pointer mine. There are at least two other north¬ 
east-southwest lodes in these workings. One of these is the New vein, which has 
been exploited in some short drifts northwest of the Mint shaft; the other is the 
Keystone lode, southeast of the Mint shaft. Neither of these has been contin¬ 
uously followed for over 200 feet on any level. They have generally northwesterly 
dips, but are branching and rather irregular fissure zones’, apparently of no great 
persistency. The New vein is in breccia and the Keystone vein, as seen in levels 
accessible from the Mint shaft, is in syenite. The latter lode probably passes into 
breccia, however, near the surface. 

CHARACTER OF ORE. 

No ore was to be seen in the Mint mine at the time of visit. The ore of the 
Pointer lode contains a gold-silver telluride, probably sylvanite, in a quartz and 
fluorite gangue. Certain portions of the lode contain galena, sphalerite, and 
tetrahedrite, often associated with rhodochrosite. The quartz, fluorite, and sylvan¬ 
ite appear to have been deposited, as a rule, after the formation of the other vein 
minerals named. The ore containing tetrahedrite and galena is usually rich in 
silver, which appears to occur chiefly in the tetrahedrite. Some of this ore is 
reported to contain over 500 ounces of silver per ton, and Stevens 0 records a state¬ 
ment of the superintendent of the Accident mine, to the effect that about 1,000 
pounds of gray copper ore from that mine contained 2,500 ounces of silver and 25 
ounces of gold. The ore being shipped by lessees from the Pointer mine at the time 
of visit was running about $53 per ton, with silver and gold present in about equal 
proportion by weight. 

PAY SHOOTS AND LODE STRUCTURE. 

The productive portion of the Pointer lode is a narrow sheeted zone in syenite, 
with a pay streak rarely exceeding 5 inches in width. The main pay shoot extends 
from a point a few feet above level 4 of the Pointer mine, or about 300 feet below 
the surface, to an unknown distance below level 7. Its maximum length of 400 
feet is attained on level 5. On level 7 the shoot is a little over 100 feet in length, 
and it is doubtful whether it continues far below the level. On the northeast the 
ore ends at the phonolite dike, the lode being of no value in the dike or in the 

a Basaltic zones as guides to ore deposits in the Cripple Creek district, Colorado: Trans. Am. Inst. Min. Eng., vol. 33, 
1903, p. 698. 



308 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

breccia beyond. There is usually one main fissure in the sheeted zone, and to this 
the ore is practically confined. It is in places as much as 5 inches in width. Some 
portions have a very open, vuggy structure, the calaverite or sylvanite occurring 
in the quartz and fluorite lining the vugs. Other portions are more solidly filled and 
contain abundant galena and tetrahedrite. Where rhodochrosite forms the princi¬ 
pal filling of the fissure the ore is of little value. 

Some small shoots of ore have been stoped from the New and Keystone lodes 
in the Mint mine, and a very little ore has been found in the Pointer lode northeast 
of the phonolite dike. 

UNDERGROUND WATER. 

These mines are at present dry, and appear never to have been seriously hampered 
by water. Information on this point, however, is not available. 

ANACONDA MINE. 

INTRODUCTION. 

The Anaconda mine is situated in the town of Anaconda, with workings extend¬ 
ing northward through Gold Hill. The property comprises about 20 claims, cover¬ 
ing 150 acres. It was originally owned by the Anaconda Mining and Milling Com¬ 
pany, which was afterwards reorganized as the Anaconda Gold Mining Company, 
capitalized at $5,000,000. In 1900, on a failure of the stockholders to respond to 
assessment, the company was reorganized as the Anaconda Mining Company, with 
a capital stock of $2,000,000. 

The mine was one of the first producers in the district, and from 1892 to 1897 
was actively worked and produced large quantities of ore, mainly from the open 
cut on Gold Hill and from stopes near the surface. In 1892 this mine was the 
largest shipper in the district and had a stamp mill of 15 tons daily capacity. For 
the past few years the property has been worked by lessees. 

PRODUCTION. 

The Anaconda mine has produced ore to the gross value of about $1,500,000, 
over $1,000,000 of this having been mined prior to the year 1900. None of the 
companies ever paid a dividend. 

UNDERGROUND DEVELOPMENT. 

The mine is at present worked through an adit (fig. 30) having its portal at 
Anaconda and connecting with very extensive drifts and crosscuts under Gold Hill. 
The adit level extends northward about 4,200 feet to the north end of the Kittie M. 
claim and connects with the workings of the Half Moon and Kittie M. shafts on the 
north side of Gold Hill. Branches of the same level extend eastward to the Colo¬ 
rado Boss ground of the Cripple Creek Consolidated Mining Company. The old 
workings from which came the ore shipped from 1892 to 1897 are all above this 
adit and for the most part not accessible. Below the adit level, or level 4, are six 
other levels. Of these, only level 10, 400 feet below the adit, is extensive. These 
lower levels are reached by a winze 1,150 feet from the adit portal. 


MINES OF GOLD HILL. 


309 


GEOLOGICAL FEATURES. 

The prevailing country rock of the Anaconda mine is breccia of the usual type 
found on Gold Hill. Within this breccia are some irregular bodies of latite-phonolite 
and a few dikes of phonolite and ‘‘basalt.” In the northern part of the adit level 
is exposed the same mass of schist that outcrops as an isolated area in the breccia 
at Fairview, on the northeast side of Gold Hill. The general distribution of the 
various rocks, so far as it lias been ascertained, is shown in fig. 30, a plan of the 
adit level. The latite-phonolite is probably intrusive into the breccia, but, as is 
so frequently the case in this district, the contacts are too indistinct to furnish 
decisive evidence on this point. A small phonolite dike sometimes accompanies 
the Anaconda lode, but is not a constant feature. There are two important basic 
•intrusions in the mine. One of these is exposed at three points on the adit level 
in the vicinity of the Excelsior shaft (fig. 30). It is apparently a rolling, irregular 
sill with a general dip of about 20°. Near the Excelsior lode the dip is easterly, 
but farther south, where the “basalt” is cut by the Anaconda lode, the dip is 
southerly. The same sill is cut on level 8, 200 feet below the adit. It seems to be 
generally parallel with the Howard “basalt” sill, but to lie from 200 to 300 feet 
vertically below the latter. If so, it may be cut in the Mary McKinney mine when 
level 6 is extended north. The other basic intrusion is a north-south dike in breccia, 
in the Colorado Boss ground. There is also a small basic dike in the breccia north 
of the syenite-porphyry mass, but it has been exposed for only a short distance. 

LODE SYSTEMS. 

The principal lodes exposed in the Anaconda mine are the Anaconda, Virginia 
M. or Lincoln, Howard Flat, Work, Excelsior, Colorado Boss, and Kittle M. or Matoa. 
They are all shown in fig. 30. 

The Anaconda lode strikes from north to X. 5° E. and dips 70° E. On the 
south, although the lode shows a tendency to split up into a number of irregular 
fissures, the general zone of Assuring probably continues into the Mary McKinney 
as the No. 2 lode. Toward the north the Anaconda on the adit level retains its 
regular course until it meets the Excelsior lode (fig. 30). The Anaconda is com¬ 
monly supposed to turn at this junction and run northeast, following in part the 
contact between the latite-phonolite and the breccia. Whether it does so or whether 
the northeast lode is a different fissure zone could not be satisfactorily determined, 
owing to the number of subordinate fissures at the junction of the Anaconda and 
Excelsior lodes. No north-south lode corresponding to the Anaconda is known, 
however, north of the Excelsior lode. In the northern part of level 10, which 
could not be visited on account of impure air, the Anaconda lode apparently curves 
to. the east before it reaches the Excelsior lode. ' 

The Excelsior lode for about 450 feet east from the Anaconda lode strikes X. 
80° E. It then turns about 20° to the south and soon becomes indistinct. West 
of the Anaconda lode the Excelsior is practically unknown. It dips about 60° N. 
The Excelsior and Anaconda lodes pass at their junction into a plexus of fissures 
within which it is impossible to determine the exact relation of one lode to the other. 

The Colorado Boss lode, worked by lessees through the Anaconda adit, is a 


310 GEOLOGY AND GOLD DEPOSITS OF THE 'CRIPPLE CREEK DISTRICT. 

mineralized north-south “basalt dike dipping about 80° E., and usually less than 
a foot wide. The general country rock is breccia. 

Probably the most important lode now worked in the Anaconda is the A irginia 
M. or Lincoln, which strikes N. 65° E. This lode is cut in the adit about 500 feet 



Fig. 30.—Plan of adit level, Anaconda mine, showing approximate distribution of rocks and position of principal lodes. 

from the portal and has been explored northwestward to the line of the Anaconda 
lode. It has also been exploited in the old Virginia M. workings, just north of the 
Anaconda adit. East of the latter lode the Virginia M. is unknown, and it has not 

































MINES OF GOLD HILL. 


311 


yet been certainly identified on the levels below the adit. The Virginia M. should 
intersect the Anaconda lode near the northwest corner of the Mary McKinney 
ground, but the present developments in this vicinity fail to show the exact relation 
of the two lodes. 

The Black or Work lode is cut in the adit about 800 feet from the portal and 
has been drifted on for over 700 feet on level 10. It strikes N. 30° W. and dips 
steeply southwest. 

Between the junction of the Anaconda and Excelsior lodes and the Kittie M. 
lode the adit level passes for nearly 2,000 feet through breccia showing no lodes of 
any importance. The Kittie M. or Matoa lode strikes about N. 23° E., and on 
the whole is vertical. Near the surface and in the Half Moon and Anchoria-Leland 
mines the Matoa lode is in breccia. On the adit level of the Anaconda, however, 
it is chiefly in schist and is less distinct than in tjie breccia. 

j 

CHARACTER OF ORE. 

The ore taken from the Anaconda and Excelsior lodes from 1892 to 1897 was 
all partly oxidized, containing free gold and some calaverite or sylvanite. Some 
of it is said to have carried 16 ounces of gold per ton, in carload lots. None of 
this ore could be seen in 1904. The ore of the Virginia M. lode is also partly oxidized 
and similar in general character to that from the Anaconda lode. A little tetra- 
hedrite, said to contain considerable gold and silver, occurs in a small fissure with 
quartz and kaolin in the breccia north of the Excelsior lode on th adit level. The 
same level near the Half Moon shaft cuts through a vein containing galena, sphaler¬ 
ite, and pyrite. These occurrences, however, have not proved of economic impor¬ 
tance, the valuable mineral of the ore of the Anaconda mine being essentially a 
telluride of gold, or free gold derived from the telluride by oxidation of the tellurium. 

PAY SHOOTS AND LODE STRUCTURE. 

The Anaconda lode is a typical sheeted zone, for the most part in breccia, but 
cutting also through latite-phonolite. Where comparatively unoxidized, as on 
level 10, the fissures of the lode are filled with small vuggy veinlets of fluorite, carry¬ 
ing as a rule little or no ore. The lode has no well-defined walls and the width of 
the sheeting varies greatly. As stope maps are not available and the old levels are 
abandoned, the Anaconda pay shoot can not be described in detail. It extended 
from the surface to within 100 to 200 feet of the adit level and probably had a 
maximum stope length of 700 to 800 feet. The ore appears to have occurred wholly 
within the zones of complete and partial oxidation. 

An isolated body of ore was stoped from the southern part of the Anaconda 
lode on the adit level and is said to have yielded $78,000. The ore, however, was a 
mere bunch and came to an end 10 feet below the level. Another little body of 
ore was taken from a short branch or spur from the Anaconda lode on level 10, and 
yielded $11,000. These occurrences show that while the original Anaconda pay 
shoot has a definite lower limit above the adit level, yet a certain amount of good 
ore may occur as bunches in the lode at any depth within the range of the present 
workings. 


312 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


The Excelsior lode in its typical portions is also a sheeted zone in breccia and 
has been stoped above the adit level. The northernmost fissure of the zone is regu¬ 
lar and persistent, so that the lode has a fairly definite hanging wall. On the adit 
level some isolated bodies of ore have been stoped from the Excelsior at points 
where it is intersected by one or more subordinate north-south fissures. 

The pay shoot wo ked in the Virginia M. lies just west of the line of the Ana¬ 
conda lode, apparently at the point where the Virginia M. is intersected by the Work 
lode. The Virginia M. here consists of two narrow" sheeted zones a few feet apart, 
in both of which small pay shoots occur. The one now being exploited is in the 
southern branch. The ore body is about 80 feet in length and pitches w-est. The 
width of the pay shoot is only 6 inches, but the ore is of high grade. It contains 
fluorite and calaverite, the latter partly oxidized to free gold. 

The Ivittie M. or Matoa lode as seen on the adit level is a zone of crushed 
and altered rock from 1 to 2 feet wide. In places it contains considerable kaolin, 
but elsewhere is a porous and somewhat limonitic mass. Some good ore was 
stoped above from the portion of the lode in breccia, near the schist. There is 
no ore, however, on the adit level. 

The Howard flat vein contains no ore in the Anaconda ground, though it 
was very productive in the Mary McKinney. It is a regular sheeted zone in breccia,. 
For about a foot in width the breccia is divided into thin sheets separated by vuggy 
veinlets of fluorite and quartz. Above and below this thinly sheeted portion the 
fissures are separated by larger and larger intervals until the vein is no longer to 
be differentiated from the country rock. From the adit level of the Anaconda it 
is possible to crawl into the old stopes near the first level of the Burke and Fry 
or Howard shaft. Here it can be seen that the ore body in the flat vein, in places 
over 6 feet in thickness, occurred where the latter is intersected by nearly vertical 
fissures. The ore occurred in the angle between the Anaconda or No. 2 lode and 
the No. 4 cross lode of the Mary McKinney mine (fig. 32, p. 323), and the approx¬ 
imately vertical fissures are probably connected w ith these lodes. 

The Work lode has the same general character in the Anaconda as in the 
Mary McKinney mine. The sheeting, as seen on level 10, is very regular and 
closely spaced. Abundant fluorite is characteristic of this lode, but it contains 
no ore except near the point where it intersects the No. 2 lode of the Mary McKinney. 

On the adit level, near the point toward which the Anaconda, Work, and 
Virginia M. lodes converge, the breccia is traversed by a great number of fissures 
of various strikes and dips. Individually these fissures are of no importance, 
though many of them contain a little calaverite. Where two or more of them 
intersect, however, there is usually a small body of telluride ore. Several such 
pockets or bunches have been discovered and are profitably exploited by lessees. 

UNDERGROUND WATER. 

All of the Anaconda workings are above the present level of underground 
w r ater, as shown in the Mary McKinney mine, and are dry except for a little water 
coming down through the old stopes. 


MINES OF GOLD HILL. 


313 


GAS. 

The mine as a whole is well ventilated and objectionable gases have little 
opportunity to accumulate. The northern part of level 10 could not be entered 
at the time of visit, on account of impure air, but this drift has only one connection 
with the surface and the air is nearly stagnant. There is apparently no con¬ 
spicuous influx of gas from the rock into the mine at any point. 

CALEDONIA MINE. 

The Caledonia is situated about a quarter of a mile northeast of Mound, on a 
low southwest spur from Gold Hill. It has been developed by three shafts and 
some irregular drifts and crosscuts. The lode strikes about N. 30° E., and has 
been explored for a length of about 500 feet and a depth of 250 feet. The general 
country rock is granite, which is cut by an irregular dike of phonolite, shown on 
the geological map (PI. II, in pocket). This phonolite turns as it is followed down, 
until at a depth of 150 feet it becomes a nearly horizontal sill extending to the 
eastv of the workings. The lode is a well-defined sheeted zone, dipping 75° or 
80° SE. It cuts through the phonolite without perceptibly faulting it. The ore 
occurred in rather irregular bunches in the phonolite or in the granite immediately 
above or below the phonolite. The maximum length of the pay shoot was about 
300 feet and practically no ore has been found at a greater depth than 100 feet. 
The ore is said to have been all more or less oxidized. The gross output of the mine 
has been about $140,000, most of which was produced in 1894 and 1895. 

CARDINAL SHAFT. 

The Cardinal shaft is situated on the point of a ridge a few hundred feet south 
of the Caledonia. The production is said to be at most 1,000 tons of ore containing 
about $20 per ton. The incline shaft descended at an angle of 70° to a depth of , 
265 feet and two levels are turned. The vein is in granite, but crosses a narrow 
phonolite dike 100 feet north of the shaft. The direction of the vein is northerly, 
the dip 70° E. A well-defined hanging wall is strongly marked by horizontal 
striations. The vein is about 1 foot wide and consists of crushed granite. A 
streak of galena was found on the hanging wall near the bottom of the shaft, also 
some calaverite. Ore has been stoped 3 feet wide for about 75 feet north of the 
shaft on level 1, but the shoot was not found on level 2. Some good ore was lately 
encountered in the bottom of the shaft. 


CHAPTER III—MINES OF RAVEN AND GUYOT HILLS. 


GENERAL INTRODUCTION. 

Ra<ven Hill lies in the southwest part of the central volcanic area. At its 
west base is the town of Anaconda and on its lower south slope the town of Elkton. 
On the southwest Guyot Hill forms a prominent spur, while on the northeast a gently 
sloping saddle joins Raven Hill with the higher Bull Hill. 

The prevailing rock of Raven Hill is phonolitic breccia, cut by numerous 
dikes of phonolite and “basalt.” This breccia is bounded on the west by Cripple 
Creek granite and on the south by Pikes Peak granite. 

The mines of Raven Hill, which are numerous and important, are mostly on 
the western and southern slopes. Between Anaconda and the summit of the hill 
is a group comprising the Morning Glory, Doctor-Jackpot, Ingham, Mattie D., 
and Elizabeth Cooper mines (PI. XXII, B , p. 292). Immediately west of this group 
is the Mary McKinney mine, with workings extending under Anaconda into Gold 
Hill. South of the Man" McKinney, on the north slope of Guyot Hill, are the 
Aileen and Katinka mines. On the south slope of Raven Hill are the Gregory, 
Tornado, Elkton, and Thompson mines, all owned by the Elkton company. On 
the southeastern slope is the Moose mine, and on the summit are the Joe Dandy 
and Ida May mines. 

DOCTOR-JACKPOT AND MORNING GLORY MINES. 

INTRODUCTION. 

The Doctor-Jackpot and Morning Glory group includes a number of mines 
which were formerly worked under individual ownership, but which are now con¬ 
trolled by three companies. The Doctor-Jackpot Company owns the Ingham, Mat- 
tie D., Jack G., Doctor, Elizabeth Cooper, Jackpot, and other claims, which were 
consolidated November 30, 1901. The Work Mining and Milling Company owns the 
Morning Glory, Morning Glory No. 2, Morning Glory No. 4, Ida B., and Little Clara 
claims. The present Morning Glory Gold Mining Company, with a capital of 
S 1,250,000, was organized in 1902 as a successor to'the Morning Glory Mining and 
Leasing Company. The new company owns the Aileen, P. C. W., Little Grant, and 
Lantishie claims and has long-term leases on the Morning Glory, Morning Glory No. 
2, Ida B., two-thirds of the Morning Glory No. 4, and the Rose Maud claims. Most 
of the work on the Work Mining and Milling Company’s property for the past few 
years has been done by the Morning Glory Company, largely through the Morn¬ 
ing Glory shaft, which was sunk under an agreement for the joint operation of the 
various claims. With the exception of the Aileen, the group thus constitutes 
practically a single mine, of which the total output is probably about $4,500,000. 
Most of this has come from the Doctor and Jackpot claims. 


314 


MINES OF RAVEN AND GUYOT HILLS. 


315 


The Morning Glory, Doctor, Ingham, and Mattie D. mines began to ship ore 
in 1893, and the Elizabeth Cooper and Jack G. in 1S95. In August, 1895, rich ore 
was found in the Doctor, and during the month of September, 1896, this mine was 
reported as shipping 600 tons of 10-ounce ore. In 1898 the Jackpot began to ship, 
and in the following year paid dividends amounting to $150,000. In 1900 the 
Doctor and Jackpot companies became involved in a legal contest for possession 
of the great ore shoot, which was settled by the consolidation, as previously stated, 
of the two companies in November, 1901. The Doctor-Jackpot mine continued 
to ship ore during 1902, but the company was much hampered in its operations 
by water. In 1903 the main pay shoot had been nearly worked out down to the 
water level and the company suspended operations. The mine is at present oper¬ 
ated by lessees. 

UNDERGROUND DEVELOPMENT. 

The workings of this group of mines are extensive, the numerous drifts and 
crosscuts penetrating a large portion of the western half of Raven Hill. The area 
exploited has a length from west to east of about 2,800 feet, and from north to south 
of about 1,800 feet. The principal access to the workings at present is the vertical 
Morning Glory shaft, near the “Low Line” station of the same name. This shaft 
is a little over 700 feet in depth and has three levels situated 100, 550, and 700 feet 
below the collar. Of these the 550-foot level is most extensive and is shown in 
fig. 31. The mouth of the Doctor inclined shaft is 950 feet east of the Morning 
Glory shaft and about 200 feet higher up the slope of Raven Hill. It follows the 
northwest dip of the Doctor-Jackpot lode down to a point about 40 feet above the 
700-foot level of the Morning Glory shaft. The Doctor levels are about 50 feet 
apart vertically, the 700-foot Morning Glory level corresponding to level 17 of the 
Doctor, and the 550-foot Morning Glory level to level 14 of the Doctor. The 
general angle or dip of the incline is 55°. The Doctor shaft house was destroyed 
by fire a year or two ago, and the incline is no longer used. None of the levels above 
10 were accessible at the time of visit. On the Jackpot claim are two shafts, one 
vertical and one inclined. The vertical shaft, 300 feet southeast of the Morning 
Glory shaft, connects with the 550-foot Morning Glory level and is still in use. A 
small shaft on the Elizabeth Cooper claim is also in use by lessees. Scattered 
over the property are a number of other shafts, such as the Ingham and Chief, 
on the Ingham lode, which are no longer in use. There are also two adits, formerly 
of more importance than now. These are the Doctor tunnel, with its portal near 
the collar of the Doctor incline; the Orehouse tunnel, which is level 1 of the Doctor 
shaft, and the Mattie D. tunnel, about 500 feet east-southeast of the Doctor incline. 
The Mattie D. tunnel follows the Mattie D. lode, which has been worked also through 
an inclined winze to a depth of nearly 300 feet below the adit level. 

The Anaconda-Raven tunnel passes through the property and connects with the 
Doctor shaft at level 5. About 700 feet northeast of the Raven is the Standard 
tunnel (not the Standard drainage tunnel), which connects with the Doctor shaft 
at level 4. 

The principal drifts of the Doc tor-Jackpot and Morning Glory mines follow 
the northeast-southwest Doctor-Jackpot lode, the longest single drift being that 


I 


% 


316 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT 





Fig. 31.—Plan of parts of underground working at Doctor-Jackpot and Morning Glory mines, showing principal lodes and 

dikes and approximate outline of the Doctor-Jackpot pay shoot. 









MINES OF RAVEN AND GUYOT HILLS. 


317 


on the 550-foot Morning Glory level, shown in fig. 31 (p. 316), which explores the 
lode for a distance of 2,900 feet. Northwest of these drifts are comparatively 
short drifts on the nearly north-south Morning Glory lode and on an intersecting 
fissure zone of the same general trend as the Doctor-Jackpot lode. East of the 
Morning Glory shaft are numerous nearly north-south drifts on the Smith-Reilly 
or Elizabeth Cooper, North Star, Walter, and Ingham lodes, and some northeast- 
southwest drifts on the Mattie 1). lode. The general plan of these drifts as seen 
on a single level is well shown in fig. 31. The principal crosscut of this group of 
workings is the Ingham, on the 550-foot Morning Glory level, which extends from 
the Morning Glory shaft to the eastern edge of the property. 

GEOLOGICAL FEATURES. 

The general country rock is breccia, of the type prevalent in Raven Hill, and 
is all indurated or otherwise altered. It contains abundant fragments of phono- 
lite and in places consists chiefly of this rock, fragments of other rocks being locally 
subordinate. No granite fragments were seen. Some of the breccia is much 
shattered, as may be well seen at the south end of the Walter drift, on the 550-foot 
Morning Glory level. The rock is here an incoherent, porous mass of angular 
fragments which are usually less than 6 inches in diameter. The loose fragments 
are not original breccia fragments, but are the result of local shattering of breccia 
previously solidified' into a firm rock. The breccia is cut by numerous irregular 
dikes and sills of phonolite which appear to have no significant relations to the 
ore. Several small basic dikes, mostly with north-south trend, are encountered 
in the Doctor-Jackpot workings. The only one of these of any economic interest 
is the North Star dike, which has produced some ore in the North Star workings, 
just north of the Doctor-Jackpot line. This dike is well exposed in the Anaconda- 
Raven and Standard tunnels. Its general course is N. 10° E., and it is practically 
vertical. It is usually 2 to 3 feet wide, but like other basic dikes in the district, 
occasionally pinches out and reappears a few feet to one side of the line previously 
followed. The rock of this dike is generally soft and decomposed. 

A feature in these mines of much interest is the presence of small quantities of 
bituminous coal in the breccia in the form of irregular bunches and veinlets. It 
occurs at several points on the 550-foot Morning Glory level, particularly in the 
Ingham crosscut near the Smith-Reilly lode. It is found also in the Doctor-Jackpot 
lode near level 15 of the Doctor, just northeast of the Doctor shaft. It here forms 
a narrow seam, 3 or 4 inches in width, filling one of the fissures of the Doctor-Jackpot 
lode and closely associated with the ore. 

LODE SYSTEMS. 

The lodes exploited in the Morning Glory and Doctor-Jackpot workings fall 
into two general classes. The first of these is a system of fissures striking nearly 
northeast and dipping to the northwest at angles of approximately 50°. Belonging 
to this class is a lode northwest of the Morning Glory shaft whose name was not 
learned, but which may be called the Galeta lode, from the Galeta inclined shaft 
sunk upon it; the Doctor-Jackpot lode; and the Mattie D. lode. The lodes of the 

13001—No. 54—06-22 


318 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


second class range in strike from north to X. 10° E. and are represented by the Smith- 
Reilly, Xortli Star, and Ingham lodes. The North Star lode is about vertical, the 
Ingham dips very steeply west j while the Smith-Reilly has a westerly dip of about 
70°. The so-called Walter lode, followed on the 550-foot level (fig. 31, p. 316), has 
a general strike of N. 15° W., and so does not belong strictly with either of the two 
main sets of lodes. Another lode, exploited on the 550-foot level about 100 feet 
east of the Smith-Reilly and called the Mattie D. lode (though its identity with the 
Mattie D. as known higher up the hill is not established), strikes X. 30° E., so that 
it is intermediate in strike between the lodes of the two general classes. Like nearly 
all the other lodes in this part of Raven Hill, it dips northwest , the angle being about 
70°. The Mattie D. lode, as seen in the Mattie D. tunnel and incline, has an average 
northwest dip of about 45°, though in some places the dip is only 20°. It intersects 
the Ingham lode, neither lode being displaced or showing any distinct difference in 
age. The relative positions of the various lodes are shown in fig. 31 (p. 316). 

The relation of the Doctor and Jackpot veins has been much discussed and 
constituted an important question in the litigation that led to the consolidation of 
the two mines. They are supposed by some to be merely parts of the same zone 
of Assuring. Others maintain that the Jackpot vein has a slightly different strike 
from the Doctor vein and is more nearly vertical. Those who hold the latter view 
believe that the Doctor and Jackpot veins intersect at a small angle and that the 
Doctor vein carries ore only at this and other intersections. At the time of visit the . 
mine workings were not in a condition to allow a satisfactory decision to be reached 
on this mooted point, and as the observed relations are most readily accounted for 
on the supposition that the so-called Doctor and Jackpot veins are really part of one 
persistent zone of Assuring, this zone will be referred to in this report as the Doctor- 
Jackpot lode. 

CHARACTER OF ORE. 

It is not possible in the present condition of the workings to give a detailed 
account of the ore of these mines. The large and rich shoots of the Doctor-Jackpot 
lode have been worked out, and accurate information concerning the character of 
ore that occurred in the abandoned stopes is difficult to obtain. In the lower 
levels, below the zone of oxidation, two fairly distinct types of ore are found in the 
Doctor-Jackpot lode. One of these shows the usual association of calaverite or 
sylvanite with quartz, Auorite, and often a little dolomite, in the veinlets of the 
sheeted zone. Some of the crystals of calaverite project into small vugs, but in 
many cases are inclosed in a compact aggregate of quartz and purple Auorite. This 
ore is by some considered characteristic of the Doctor lode. The other type is 
characterized by the presence of tetraliedrite, associated with pyrite, quartz, and 
dolomite, but with little or no Auorite and, so far as observed in the few specimens 
obtainable, no visible tellurides. Some of the specimens of this ore show a deAnite 
mineralogical sequence. Pyrite and tetrahedrite crystalized Arst on the walls of the 
Assures, accompanied by a mineral, probably celestite, crystallizing in rather slender 
prisms of rhombic cross section. Deposition of quartz, with sometimes a little 
Auorite, followed, and during this deposition the prismatic mineral was altered to 
hollow siliceous pseudomorphs. The alteration seems to have consisted in a partial 


MINES OF RAVEN AND GUYOT HILLS. 


319 


external silicification of the unknown mineral, with subsequent solution and removal 
of the unsilicified core. Finally pyrite was deposited in small sharp crystals upon 
the surfaces of the quartz crystals. Other specimens show that the fissure walls 
were in part coated with crystals of dolomite upon which are implanted tetrahedral 
crystals of tetrahedrite associated with a little pyrite. This second type of ore is by 
some considered characteristic of the Jackpot lode. 

Some of the tetrahedrite ore being stoped by lessees on level 15, near the 
Doctor shaft, contained from 6 to 27 ounces of silver per ton, while some ore previ¬ 
ously extracted was said to contain up to 200 ounces of silver and 20 ounces of gold. 
At this point in the mine a seam of coal (see also p. 31) lies along the foot wall of the 
tetrahedrite ore and is stoped with the latter. The coal is reported to have given 
an assay value of $40 per ton in gold, but it is doubtful whether the sample was 
taken with sufficient care to avoid including some of the adjacent ore. 

The ore now mined by lessees from the Smith-Reilly lode and associated 
fissures is of the usual type—calaverite associated chiefly with quartz and fluorite 
in narrow cracks in the breccia. 

PAY SHOOTS AND LODE STRUCTURE. 

The Doctor-Jackpot lode is a remarkably w r ell-defined and regular zone of 
parallel Assuring. It has been followed on the 550-foot Morning Glory level for 
2,900 feet, and is without doubt one of the most distinct and persistent sheeted 
zones in the district. In its typical development, as seen on the 700-foot level 
northeast of the Morning Glory shaft, the lode consists of two regular and well- 
defined parallel fissures from 3 to 6 feet apart. These fissures, particularly the 
foot-wall fissure, exhibit more evidence of movement of the w r alls than do most of 
the Cripple Creek lodes, and some slickensided surfaces w r ere observed, but not such 
as to indicate any great displacement. Between the tw o main fissures the breccia is 
usually sheeted, or divided into thin slabs of an average thickness of 2 or 3 inches 
by minor parallel fissures, and close examination often reveals less conspicuous 
cracks dividing these slabs into still thinner plates. The fissures of this sheeted zone 
are not all filled with the same material. Some are occupied by veinlets composed 
chiefly of a fine-grained purple aggregate of quartz and fluorite, locally inclosing 
calaverite. Others contain dolomite and quartz with tetrahedrite and a little 
fluorite, and still others are filled with rather crumbling aggregates of pyrite. In 
some cases the veinlet forms a fairly solid filling, but in others it is more or less open 
and vuggy. The lode varies from point to point in w T idth and in the number and 
disposition of its constituent fissures. In some places there is little more than a 
single w^ell-defined fissure. In others the fissures diverge so as to inclose horses of 
country rock as much as 30 feet in width. Such a horse appears in the northeastern 
part of the 700-foot level, where the stronger hanging-wall zone is sometimes called 
the Doctor lode, wdfile the foot-wall zone is called the Jackpot lode, and contains 
tetrahedrite. Somewhere below the 550-foot Morning Glory or Doctor level 14 these 
two zones of Assuring appear to join and form a single well-defined lode. Near the 
Doctor level 10, however, in the vicinity of the Doctor shaft, the lode again shows 
two sheeted zones separated by a horse of breccia with a maximum width of about 


320 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


30 feet. The main stupes, coming from below, follow the northwest or hanging- 
wall branch of the lode, though the foot-wall branch has been stoped to some extent 
just above level 10. At both ends of level 10 the two fissure zones approach each 
other, but the level has not been carried far enough to determine whether they 
actually join on the lines of strike. Owing to the bulkheading of the Doctor shaft 
near its mouth, the levels above 10 and below 1 were fdled with gas at the time of 
visit, and no further observations could he made on the relations of the supposed 
Doctor and Jackpot lodes. 

The pay shoots of the Doctor-Jackpot lode occupy but a small part of the whole 
length of the lode. The ore forms at least two distinct shoots, one coming to the 
surface near the Doctor shaft and one near the Jackpot shaft. They may be con¬ 
veniently distinguished as the Doctor and Jackpot pay shoots. The Doctor pa}' 
shoot lies for the most part east of the North Star basaltic dike and has been worked 
chiefly from the Doctor and Orehouse tunnels, and probably from the now inaccessi¬ 
ble northeast drifts on the Doctor levels 2 and 4. Some of the ore was seen at the 
northeast edge of the old stope, about 50 feet below the Orehouse tunnel, where 
lessees were working at the time of visit. This ore is partly oxidized, showing 
calaverite and free gold, but no tetrahedrite. The best of it, a narrow oxidized 
seam along the hanging wall, was said to carry about 3 ounces of gold per ton. The 
depth to which this pay shoot extended could not be ascertained at the time of visit, 
but it apparently ended well above the Anaconda-Raven tunnel, or Doctor level 10. 
Below it the Doctor shaft went through a nearly barren part of the lode until it 
reached the Jackpot shoot, near level 12. The Jackpot pay shoot has an unusually 
low northeast pitch, probably considerably less than 30°, which carries its upper 
limit from the surface near the Jackpot shaft to level 12 at the Doctor shaft. The 
maximum length of this pay shoot on any one level was from 400 to 500 feet, and on 
the Doctor level 15 it was stoped for 225 feet in length. It has been stoped practi¬ 
cally from the surface to the 700-foot Morning Glory level, though there are compar¬ 
atively barren portions just above the latter level and near the Doctor levels 10 and 
14. Exploitation below the 700-foot level has hitherto been impracticable on 
account of water. The width of the ore in the Jackpot shoot below the Doctor level 
10 varies from 5 to 10 feet, being widest where small cross fissures intersect the main 
lode. This is the principal pay shoot of the property and the question of its owner¬ 
ship was the subject of the legal contest which in 1901 resulted in the consolidation 
of the Doctor and Jackpot mines. 

No work has been done for some time on the Morning Glory lode and very little 
could be seen in these old workings at the time of visit. Penrose® describes the lode 
as a well-developed sheeted zone cutting breccia and phonolite, the ore containing 
gold telluride and free gold associated with quartz and fluorite. lie refers to the 
presence of several northeast-southwest fissures which we now know to be generally 
parallel with the Doctor-Jackpot lode. 

The Ingham lode is an irregular zone of Assuring in phonolitie breccia. The 
principal pay shoot in this lode occurred between the Ingham and Gregory shafts, 
and is said to have attained its greatest width, 20 feet, in the vicinity of a small 

oMining geology of the Cripple Creek district, Colorado: Sixteenth Ann. Rept. U. S. Geol. Survey, pt. 2, 1895, 
pp. 188-189. 



MINES OF RAVEN AND GUYOT HILLS. 


321 


basalt dike crossed by the lode. This dike, however, could not be found at the time 
of visit, nor was any of the ore visible. The latter is reported to have been partly 
oxidized, containing free gold and tellurides, and to have been worth $35 to $40 per 
ton. No ore has been found on the Ingham lode on the 550-foot Morning Glory 
level, and the lode below this is unexplored. 

The Mattie D. lode is structurally very similar to the Doctor-Jackpot, with an 
even and well-defined hanging wall. Along this hanging wall is usually a few inches 
of brecciated rock indicating some tangential displacement of the walls, although 
the lode does not perceptibly fault the Ingham lode. There are, as a rule, two or 
three other fissures parallel with the hanging-wall fissure, the average width of the 
lode being about 3 feet. Several small pay shoots have been stoped on the Mattie 
D. lode, but no large body of ore. 

The Walter vein, as known in the Doctor-Jackpot mine, has been explored 
chiefly on the 550-foot Morning Glory level, with negative results. It is a rather 
obscure fissure zone cutting the breccia and several phonolitic intrusions. 

The ore in the North Star lode occurred in the altered basalt of the North Star 
dike within 300 feet of the surface and was worked chiefly through the old North 
Star shaft, now abandoned. Its occurrence was described by Penrose." 

Considerable ore has been stoped between the surface and the 550-foot Morr'ng 
Glory level from short pay shoots in the Smith-Reilly lode and in some small associ¬ 
ated cross fissures. This ore is partly oxidized, carrying free gold and tellurides. 
So far as known these pay shoots do not extend to the 700-foot level. 

UNDERGROUND WATER. 

The first water reported in these mines was at a depth of about 600 feet below 
the collar of the Morning Glory shaft, or 9,121 feet above sea level, and was encoun¬ 
tered in 1900. As the Standard tunnel, with its face 9,056 feet above sea level, had 
at this time passed its maximum discharge and as the deeper Mary McKinney mine 
had been actively pumping, the water in the Morning Glory shaft evidently stood 
considerably below its natural local level. The maximum flow was reached at the 
700-foot level (9,021 feet above sea level) in 1901, when the pumps raised 1,890 
gallons per minute. In the summer of 1902 steady pumping had lowered the water 
level 100 feet and pumping, being no longer necessary to keep open the 700-foot 
level, was discontinued. Since then the water has very slowly receded in the sump, 
the rate, according to Mr. V. G. Hills, being 0.03 foot per day. In July, 1903, the 
water in the sump was 2 feet below the 700-foot level. 

mary McKinney mine. 

INTRODUCTION. 

The Mary McKinney mine is situated on the south side of Squaw Gulch, oppo¬ 
site the town of Anaconda. Adjacent mines are the Anaconda and Peggy on the 
north, the Morning Glory and Doctor-Jackpot on the east, and the Katinka and 
Aileen on the south. The property comprises the Mary McKinney, Mary McKinney 


a Sixteenth Ann. Rept. U. S. Geol. Survey, pt. 2, 1895, p. 188. 








322 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

No. 2, Republic, Mayflower, Le Clair, and Thurlow claims, and covers about 34 
acres. It is owned by the Mary McKinney Company, of Colorado Springs, incor¬ 
porated in 1892, and capitalized at $1,000,000. Up to the beginning of 1889 the 
mine was worked by lessees, the first shipment of ore being in 1893. Early in 
1899 the company began operations^ on its own account, and erected the present 
shaft house. The first dividend was declared in October of the same year. 

The mine has produced a large amount of ore and has undoubtedly been 
profitable to the company Statistics of production, however, are not obtainable. 

UNDERGROUND DEVELOPMENT. 

The main shaft, 609 feet deep, is on the Republic claim, about 1,000 feet 
from the south end of the property. There are four other smaller shafts, of which 
the only one now in use is the Burke and Fry shaft, in the northern part of the 
mine, operated b}^ lessees. 

There are five main levels, which at the shaft are approximately 135, 210, 
280, 380, and 485 feet below the surface. These extend through the Republic and 
Mary McKinney claims in a general north-northeast direction, practically from 
one end of the property to the other. In the southern part of the mine the drifts 
are of simple linear plan, following the Mary McKinney and Le Clair lodes, which 
intersect at a small angle. In the northern part of the mine, however, the work¬ 
ings, as may be seen from fig. 32, are more complex, owing to the less regular char¬ 
acter of the Assuring and to the existence of a number of so-called “flat veins,” 
some of which are shown in fig. 33. The Ophelia tunnel passes through the 
northern end of the mine, 15 or 20 feet above level 4. 

GEOLOGICAL FEATURES. 

The workings of the Mary McKinney mine are mainly in breccia and phonolite. 
Although on the surface the granite-breccia contact is less than 400 feet west of 
the shaft, it was seen at only one point in the mine, in a west crosscut on level 4, 
south of the shaft. It is here fairly distinct and seems to be about vertical. It 
is probably cut also in an old unused adit connecting with level 1. 

The main country rock of the mine from the south end to a point about 1,200 
feet north of the shaft is phonolite, varying in texture from the greenish aphanitic 
variety, common in the dikes and smaller intrusive masses of the district, to tra- 
chytic facies showing phenocrysts of feldspar and pyroxene. The form of this 
phonolitic mass can not be even approximately determined from existing workings. 
It does not appear to reach the surface, though it is the principal rock of all the 
levels from 1 down. The crosscut into the granite on level 4 shows breccia between 
the phonolite and the granite, but the contact between the phonolite and breccia 
is very obscure. In the northern part of the mine the contact is comparatively 
sharp and regular. It strikes nearly east and west and dips 85° S. On level 4 it 
has the appearance of an intrusive contact, but on level 3 this relation, if, as seems 
probable, it is the true one, is obscured by the abundance of phonolite fragments in 
the adjacent breccia. 

One of the most interesting geological features in the northern part of the 
mine is a sill, or recumbent dike, of trachydolerite, locally known as the Howard 


MINES OF RAVEN AND GUYOT HILLS. 



Fig. 32.—Plan of the veins of the Maiy McKinney mine, level 4. 






























324 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

dike, or Mary McKinney “flat vein.” This strikes approximately northwest and 
southeast, and dips southwest at an average angle of 20°, which is about the same 
as the slope of Gold Hill. It is cut in the Burke and Fry shaft 400 feet below the 
surface. On level 3 it appears about 50 feet north of this shaft, in the breccia. It 
is here about 4 feet in thickness and has a higher dip than usual. Toward the 
north it passes about 75 feet above the Ophelia tunnel at the point where the latter 
cuts what is known as the No. 2 vein of the Mary McKinney mine. The basic sill 
exposed in the Ophelia tunnel about 3,900 feet from the portal is probably the 
same as that known in the Mary McKinney mine. The more conspicuous sill 
exposed from 4,600 feet to 4,800 feet in from the portal is apparently a second 
and lower sheet of “basalt” which seems not to have been encountered as yet in 
the Mary McKinney workings. On level 4 of the Mary McKinney the Howard 
sill occurs about 200 feet south of the Burke and Fry shaft and is here in phonolite. 
It is about 3 feet thick on this level. On level 5 the trachydolerite is cut about 
425 feet south of the Burke and Fry shaft, and has been followed for over 300 feet 
in a curved drift. Here also it is in phonolite. A general idea of the geological 
relations in the Mary McKinney mine maybe had from fig. 32 (p. 323), which is a 
map of level 4. 

LODE SYSTEMS. 

The horizontal relations of the principal lodes are shown in fig. 32. On all 
the levels the Mary McKinney lode maintains its usual regularity from near the 
south end of the property to within about 200 feet from the contact between the 
phonolite and breccia, in the northern part of the mine. South of the shaft the 
lode strikes N. 9° E. North of the shaft, however, it curves gently eastward until 
it strikes N. 25° E. The dip is westerly and ranges from 65° to 75°. 

The Le Clair is a vertical lode, striking N. 6° E., and intersecting the Mary 
McKinney lode at an acute angle. On level 2 the crossing of the two lodes is well 
shown and is about 200 feet south of the shaft. Neither lode appears to displace 
the other at the crossing, nor is there any indication of one lode being older than 
the other. On level 3 the intersection occurs about 100 feet south of the shaft. 
On level 4 the lodes cross about 275 feet north of the shaft, but continue close 
together and apparently coalesce near the shaft. At 175 feet south of the shaft a 
fissure zone turns off to the south and has been followed for over 100 feet in a 
drift. This is probably the Le Clair. If so, the two lodes practically coincide on 
this level for a distance of over 400 feet. On level 5 the Mary McKinney and 
Le Clair lodes join 375 feet north of the shaft, run together for about 100 feet, and 
then gradually diverge. They appear to meet again near the shaft. South of the 
shaft on this level the Le Clair is unknown. It has been explored for a total length 
of about 1,000 feet. At several points the Mar}^ McKinney lode is crossed at 
acute angles by other fissures similar to the Le Clair, but of less persistency and 
carrying much smaller values. 

In the southern part of the mine these two lodes are the only ones of economic 
importance. In the northern part, however, the Assuring, as already stated, 
becomes more complex, as may be seen from fig. 32 (p. 323). As the Mary McKin¬ 
ney lode is followed north it shows a tendency to split up near the contact between 


Fig. 33.—Generalized longitudinal section of the Mary McKinney mine, showing relation of flat veins and Howard basic dike. 


MINES OF RAVEN AND GUYOT HILLS. 


325 
































326 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


the phonolite and breccia and to turn northeasterly. Beyond this turn it becomes 
increasingly difficult to follow. As the Mary McKinney lode loses in distinctness 
another lode, lying east of it, becomes prominent. This is the No. 2 vein, striking 
generally N. 20° E. Unlike the Mary McKinney, it dips easterly, the angle ranging 
from 80° to 85°. The lode continues northward under the Howard flat into the 
Anaconda mine, and is there known as the Anaconda vein. The farthest point 
south to which the No. 2 vein has been followed is on level 5, about 500 feet south 
of the Burke and Fry shaft. In a general way its importance diminishes as the 
Mary McKinney lode west of it becomes more regular and distinct. 

Linking the No. 2 lode with the Mary McKinney lode is the No. 1 vein. This 
is a rather irregular and somewhat indistinct fissure zone striking northeast and 
dipping northwest at varying angles. It is not known to extend west of the Mary 
McKinney lode, though it apparently crosses the No. 2 lode. 

In addition to the lodes of meridional to northeasterlv trend, the mine contains a 
number of cross lodes. One of these, south of the shaft (fig. 32, p. 323), is known 
as the Jackpot vein though not the same as the productive lode of the Doctor- 
Jackpot mine. This strikes about N. 80° W. and dips north at an angle of about 50°. 
It is faulted by the Mary McKinney lode. The throw can scarcely exceed 10 or 15 
feet and the displacement corresponds to a reversed fault. About 100 feet and 250 
feet north of the main shaft the Mary McKinney and Le Clair lodes are crossed by 
two approximately vertical cross veins, striking N. 60° W. No displacement of 
any of the lodes can be discovered at the crossings. One of the most important 
cross veins in the mine is known as the No. 4 vein, and crosses the Mary McKinney 
No. 1 and No. 2 veins in the vicinity of the contact between the phonolite and the 
breccia. Tins lode strikes N. 31° W. and dips 85° SW. No perceptible faulting 
occurs at its intersections with the other lodes. About 300 feet northeast of the 
No. 4 lode is the parallel Black or Work vein, a persistent sheeted zone which is 
known also in the Anaconda mine and in the Ophelia t nnel. 

The northern part of the Mary McKinney mine contains a number of so-called 
“flat veins” with generally northerly dips of less than 45°. One of the most inter¬ 
esting of these is the Howard flat vein. Were it exposed at the surface this lode 
should outcrop about 150 feet south of the Burke and Fry shaft. It is cut in this 
shaft 150 feetsbelow the surface and dips about 30° N. It lies above the present 
accessible workings of the Mary McKinney mine, but can be well seen in the 
Anaconda and Ophelia workings. Two hundred feet vertically below the How¬ 
ard flat vein is the generally parallel No. 7 flat vein, which is well exposed on level 3, 
just north of the Burke and Fry shaft. About 200 feet below the No. 7 flat is the 
No. 3 flat vein, and about 40 feet below the latter is the No. 5 flat vein. Between 
the named members of this system of generally parallel flat veins dipping north 
at angles from 20° to 40° are a number of other fissures which have not been recog¬ 
nized as distinct lodes. The breccia in the northern part of the mine is thus charac¬ 
terized by well-marked parallel sheeting, the planes of this sheeting having a general 
northerty dip of about 30°. As a rule the nearly vertical fissure zones intersect 
this sheeting and the Howard basalt dike without appreciable faulting. In one 
case only was faulting observed. This was on level 3, where a small, unimportant 
vertical fissure faults the No. 7 flat vein with a throw of 4 or 5 inches. 


MINES OF RAVEN AND GUYOT HILLS. 


327 


PAY SHOOTS AND LODE STRUCTURE. 

The principal pay shoot is in the Mary McKinney lode, a regular sheeted zone 
in phonolite. This shoot has been stoped from the surface to level 5 and for a 
length of nearly 2,000 feet. Although portions of the lode have proved to be of too 
low grade for stoping, yet the sheeted zone constitutes an essentially continuous 
ore body from a point 700 or 800 feet south of the shaft north to the contact of the 
phonolite. In other words, where the fissuring is regular and distinct it usually 
carries ore. Some bodies of ore occur in the Mary McKinney sheeted zone in the 
breccia, but these can hardly be considered as belonging to the main pay shoot. 
The lode on the whole is rather narrow, stupes over 5 feet in width being apparently 
exceptional. At the time of visit, however, the Mary McKinney lode had been 
nearly worked out down to level 5 and there were few opportunities of studying 
the occurrence of the ore. There is usually a main fissure up to 4 or 5 inches in 
width, carrying quartz and dark, compact fluorite and showing vuggy cavities in 
its medial plane. Where such vugs occur, and particularly where roscoelite is 
associated with fluorite, the ore is usually good and crystals of calaverite may be 
seen in the vugs and embedded in the quartz and fluorite. This relation, however, 
does not hold everywhere, for certain vuggy portions of the lode, containing much 
roscoelite, are too poor to pay. Associated with the main fissures are others of less 
persistency. Some of these are parallel with the main fissure, while others are of 
irregular character. These subsidiary fissures usually contain quartz and fluorite 
and some of them carry calaverite and tetrahedrite. According to Superintendent 
Buckles there is a definite relation between the tenor of the ore and the character 
of the jointing on the hanging-wall side of the lode. Where the joints dip gener¬ 
ally east or into the lode the ore is good. Where they dip west or away from the 
lode the ore is poor. 

The Le Clair lode is similar to the Mary McKinney in structure and mineralog- 
ical character, but the pay shoot is much shorter. It nowhere extends for more 
than 500 feet from the intersection with the Mary McKinney lode, and as a rule 
ends within a much shorter distance. 

The northern part of the mine contains a number of short pay shoots, some in 
the nearly vertical lodes, some in the flat veins, and some at points of intersection 
of two or more zones of fissuring. 

The No. 2 lode is a sheeted zone of the usual type, in which the ore occurs 
rather erratically to a maximum width of about 12 feet. At the north end of 
level 4 the fissures of the sheeted zone are abundant and narrow, the calaverite 
occurring in them and in the more irregular joints of the breccia, associated with 
thin films of fluorite much as in the Captain stopes of the Portland mine. Short 
pay shoots occur also in the No. 1 lode and in the No. 4 cross lode. These are min¬ 
eralized sheeted zones of the usual type, the ore consisting of calaverite in the 
narrow fissures cutting either breccia or phonolite. The No. 1 lode is not a regular 
sheeted zone, but is composed of a number of such zones of slight individual 
persistency which intersect at small angles. It thus shows frequent variation in 
strike and dip and the ore occurs in isolated bunches. Some of the flat veins, 
particularly the No. 3, have proved individually productive. The No. 3 flat vein 


328 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


where stoped between levels 3 and 5 consists of a sharply distinct veinlet of fluorite, 
quartz, and calaverite rarely more than an inch in width. This is usually asso¬ 
ciated with a little parallel sheeting of the breccia, but the value of the ore lies 
almost wholly in the small veinlet, which in spite of its diminutive size is rich 
enough to stope. The calaverite occurs chiefly along the sides of the veinlet and 
and in the medial quartzose vugs. 

The main interest in the northern part of the mine centers in the occurrence 
of ore bodies at various intersections of lodes with each other and of lodes with the 
Howard dike. Such a body occurs just above level 4, where a triangular portion 
of the “basalt” bounded on the northwest b}” the Mary McKinney lode, on the 
northeast by the No. 4 cross lode, and on the south by the contact plane between 
the breccia and phonolite carried enough calaverite in the innumerable minute 
fissures or joints of the rock to constitute an important pay shoot. A similar 
though less extensive mineralization of the dike occurs between levels 3 and 5 along 
the intersection with the No. 2 lode. 

Another important pay shoot occurs at the Burke and Fry shaft on level 5> 
along the line of the No. 2 lode. This body of ore is about 250 feet in length and 
has a maximum width of about 40 feet. The ore does not extend more than 15 
or 20 feet above the level, but how far it goes below is not yet known. The ore 
body occurs where a number of fissures, including the No. 2, Work, No. 6, No. 3, 
and No. 5 flat veins intersect. In the vicinity of this intersection the breccia is 
elaboratelv fissured. In addition to the named sheeted zones, there is also a 
pronounced local sheeting with a dip of about 35° S., a system of fissures generally 
parallel with the No. 2 lode, and much irregular jointing. The ore occurs not only 
in the intersecting lodes, but in practically all of the immediately adjacent fissures, 
forming a body of irregular shape with no definite boundary separating it from the 
breccia country rock. The value lies in the fissures, in the form of calaverite 
associated with thin films of quartz and fluorite. 

The Work lode is of no economic importance in the Mary McKinney mine except 
at the intersection with the No. 2 lode. It is, however, a strong, prominent vein, 
locally showing over a foot of fluorite and quartz between well-defined walls. This 
vein is usually accompanied by parallel sheeting of the breccia. In some portions 
the filling is chiefly dark, compact fluorite, whence the name Black vein. Else¬ 
where the filling is chiefly quartz with abundant open vugs. This quartz is clear 
and vitreous, resembling that described in the Howard flat vein, in the Ophelia 
tunnel, and Anaconda mine. The Jackpot lode is also a well-defined sheeted zone, 
but contains only small bunches of ore at the intersection with the Mary McKinney 
lode. 

CHARACTER OF ORE. 

The principal gold-bearing mineral of the Mary McKinney mine is calaverite, 
which occurs associated with quartz, fluorite, dolomite, roscoelite, tetrahedrite, 
and pyrite. So far as observed the calaverite is found only in the fissures, never 
within the unfissured country rock. Pyrite, on the contrary, is widely disseminated 
through the country rock. In the breccia of the northern part of the mine some 
of the calaverite occurs with mere drusy films of quartz or fluorite in extremely 


MINES OF RAVEN AND GUYOT HILLS. 


329 


narrow cracks or joints, the ore thus resembling that found in the Captain stopes 
in the Portland mine. The ore occuring in “basalt” is apparently of similar 
character, although very little of this ore was visible at the time of visit. 

Usually, however, the calaverite occurs in distinct vein lets of quartz and 
fluorite ranging in width from a fraction of an inch up to about 6 inches. The 
quartz and fluorite often show comb or vug structure, but sometimes form a solid, 
compact vein. The best example of such compact vein matter is furnished by 
the Work vein, much of which consists of a dark-purple fine-grained aggregate of 
quartz, fluorite, and a carbonate—probably dolomite. This material, however, is 
rarely sufficiently auriferous to be ore. Although the calaverite occasional^ pro¬ 
jects into the vugs, it is more commonly entirely inclosed in the gangue minerals. 
An earthy green mineral, determined by Doctor ITillebrand to be a vanadiferous 
silicate, probably roscoelite, is abundant in portions of the Mary McKinney vein 
and usually, though not always, indicates good ore. It occurs particularly near 
the walls of the veinlets and as an alteration product of small fragments of country 
rock inclosed in the quartz and fluorite. 

Tetrahedrite occurs in massive form in the Mary McKinney vein a few feet 
below level 5. It is found in close association with calaverite in little stringers of 
quartz and fluorite in phonolite. Some of the stringers contain a little dolomite, 
and hollow siliceous pseudomorphs after celestite occur in occasional small vugs. 
There can be no question that in this case calaverite, tetrahedrite, quartz, and 
fluorite all crystallized contemporaneously. 

There is very little oxidation in the Mary McKinney mine below a depth of 
200 feet and no oxidized ore is now being produced. 

UNDERGROUND WATER. 

Water was originally encountered in the Mary McKinney at an elevation of 
9,498 feet above sea, or at a depth of only 35 feet below the collar of the shaft. 
In 1899, owing to the lowering of the water by pumping and by the Ophelia and 
Standard tunnels, the level stood at 9,241 feet above sea, or 292 feet below the 
collar of the shaft. About this time level 5 was opened, but owing to the excessive 
water was soon afterwards temporarily abandoned. It was not recovered until 
April, 1901, when the Elkton is reported to have been pumping 1,200 gallons per 
minute in order to regain its level 8 . The water continued to fall and in January, 
1903, stood at 9,023 feet above sea, or about 10 feet below level 5, and was going 
down at the rate of 0.03 foot per day . a 

Upon the opening of the El Paso drainage tunnel on September 6 , 1903, the 
water began to fall more rapidly, the record being as follows: 

Recession of water in Mary McKinney mine after opening of El Paso drainage tunnel. 

- ' Inches. 


First week.29. 00 

Second week.-. 17. 00 

Third week.-.-. 10. 00 

Fourth week.- - 8. 00 

Fifth week. 7. 25 


a mils, V. G., Ninth Ann. Rept. Portland Gold Mining Company, 1903, p. 91. 

\ 










330 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


When the mine was visited on January 12, 1904, the water was about 35 feet 
above level 6, or about 8,988 feet above sea. On April 17 the water was 31 feet 
lower and its recession was being hastened by pumping 360 gallons a minute. 

PEGGY MINE. 

The Pegg}^ is of interest as being one of the most recently developed mines 
in the district, work having begun early in 1903 on the Sunset, a small fractional 
claim surrounded by the properties of the Mary McKinney, Work, Rose Maud, 
and Cripple Creek Consolidated mining companies. While really in Gold Hill, 
the mine is so closely related to the Mary McKinney mine as to be best described 
in this place. The shaft, situated in the town of Anaconda, is about 361 feet deep, 
with two small levels, one 300 feet and the other 361 feet below the collar. The 
workings are all in breccia. The shaft was sunk in the expectation of finding ore 
at the intersection of a nearly north-south fissure with the Howard dike or sill. 
At a depth of 300 feet, however, a flat vein was encountered, striking about N. 
70° E. and dipping 45° N. This can scarcely be the Howard flat vein, but may 
possibly be what is known as the No. 3 flat vein in the Mary McKinney mine. 
The Peggy vein consists of a little veinlet of fluorite, usually only an inch or two 
wide, accompanied by minor parallel fissures. The ore occurs as calaverite or 
sylvanite, chiefly in the fluorite of the main veinlet, but also to some extent in the 
accompanying fractures. The best ore is said to occur near the intersection of the 
Peggy vein with the nearly north-south fissure passing through the shaft. The 
ore is said to carry from 4 to 10 ounces of gold per ton. Stoping had barely begun 
at the time of visit, and the present level 2 had not been opened. Lessees 
working through the Peggy shaft have opened a good body of ore on the south 
end of the Colorado Boss No. 3 claim, just north of the Peggy ground. This ore 
occurs as calaverite in a number of small irregular fissures of various dips, but 
striking generally N. 25° E. These fissures are in the hanging wall of the flal 
Peggy vein, which becomes very indistinct in their vicinity. 

KATINKA MINE. 

The Katinka Gold Mining Company, capitalized at $1,250,000, owns the 
Katinka, August Flower, Chicken Hawk, and Hobo claims on Guyot Hill, immedi¬ 
ately south of the Mary McKinney mine. The mine is operated by lessees. The 
underground workings comprise a crooked incline about 600 feet in depth, with 
seven short and unsystematic levels. There is also a vertical shaft, which, however, 
is not connected with most of the levels and is not used. 

The Katinka lode is a somewhat irregular southerly continuation of the Mary. 
McKinney lode. The country rock is chiefly breccia, which lies between the 
intrusive phonolite mass of the Mary McKinney mine and the granite of the south¬ 
west side of Guyot Hill. The breccia contains many granitic fragments and is 
cut by several phonolite dikes. The only important ore body of the Katinka 
occurs near the Mary McKinney line from 400 to 500 feet below the surface. It 
is the south end of an ore shoot stoped in the Mary McKinney mine above level 3. 
The production of the Katinka mine is not known, but can not have been large. 


MINES OF RAVEN AND GUYOT HILLS. 


381 


ELKTON MINE. 

INTRODUCTION. 

The Elkton property is owned by the Elkton Consolidated Mining and Milling 
Company, of Colorado Springs, capitalized at $3,000,000. When visited by Pen¬ 
rose in 1894 it was a small mine, 200 feet in depth, with workings confined to the 
Elkton and Kentucky Bill claims. In 1898 the company bought the Appie Ellen 
mine and in 1899 the Thompson. In 1900 the Raven mine, one of the first locations 
in the district, and the Tornado mine were consolidated with the Elkton. The 
Gregory mine was subsequently acquired and the Elkton property now stretches 
northward from the village of Elkton, between Arequa and Eclipse gulches, past 
the summit of Raven Hill. In this irregular north-south strip, over 4,000 feet in 
length, are embraced the Thompson, Raven, Walter, Snide, Katherine, Gregory, 
Princess E., and a number of other claims. The main shaft, situated in Elkton, 
is well equipped with a steel gallows frame, first-motion flat-rope hoist, and 40-drill 
compressor. While the Thompson, Tornado, and Gregory are really separate 
mines, they are so closely connected with the Elkton proper that, in this report, 
all may be conveniently included under the name Elkton mine. 

PRODUCTION AND DIVIDENDS. 

The production and dividends of the Elkton mine, so far as they are obtainable, 
are given in the following table. The figures, however, do not include the output 
of the Raven and Gregory mines prior to their consolidation with the Elkton. No 
separate account was kept by the company of the small amount of silver in the ore. 


Production and dividends of the Elkton mine. 


Year. 

Gross value. 

Gold. 

Dividends. 

Year. 

Gross value. 

Gold. 

Dividends. 

1893. 

$18,759. 76 

Ounces. 

937.98 


1899. 

$617,308.29 

Ounces. 

30,865.41 

$63,750.00 

1894. 

113,602. .50 

5,680.12 

$41.546.57 

1900. 

1.029,260.59 

51,463.02 

258,758.00 

1895. 

79,019.65 
463,732.02 

4,850.98 
23,186.60 


1901. 

1.044,017.88 

493,248.28 

52,200.89 
24,662. 41 

325.000.00 

1890. 

100,000.00 

1902 . 

100.000.00 

1897 

555,164. 78 

27.7.58.23 

270,000.00 

220.000.00 

1903. 

533,409.14 

26,670. 45 


1898. 

552.982.15 

27,649.10 




UNDERGROUND DEVELOPMENT. 

There are four important shafts on the Elkton property, three of which, the 
Thompson, Elkton, and Tornado, lie on a nearly due north-south line, while the 
Gregory lies a little east of that line. (See PI. Ill, in pocket.) The principal drifts 
run north and south, following the Walter lode, but there are also important north- 
northwest drifts on the Raven lode and some very irregular workings in granite 
near the Thompson shaft. (See fig. 34.) 

The main Elkton shaft is 800 feet deep and connects with eight levels about 
100 feet apart (fig. 35). The Thompson shaft, 700 feet south of the Elkton, connects 
with Elkton levels 4 and 5, the latter being the bottom of the shaft. The Tornado 






























332 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


shaft, 1,300 feet north of the Elkton and 390 feet higher, is about 875 feet deep, the 

___ ninth or bottom level being the Elkton level 5. 

I* - The Gregory shaft, 850 feet north-northeast of 

the Tornado and 163 feet higher, is 680 feet in 
depth, its bottom level being the Anaconda- 
Raven tunnel. This tunnel runs from Anaconda 
under Raven Ilill, in a direction S. 57.5° E. to 
the Gregory shaft. It then continues eastward 
until it cuts the Raven dike, about 200 feet from 
the Gregory shaft, and follows this dike for about 
900 feet to the south-southwest, connecting near 
the Tornado shaft with the main Elkton and 


Tornado shaft 


N 

M 



Tornado workings. 


LODE SYSTEMS. 


Stopes at fissure 
intersections 


BRECCIA 


Elkton shaft 


Stopes on vein 



The principal lode in the Elkton property is 
the remarkably regular Walter vein, one of the 
straightest and most persistent zones of Assuring 
in the district (fig. 34). Its general strike is 
N. 1 ° E. Near the Elkton shaft the Walter 
lode dips east at angles ranging from a mini¬ 
mum of 75° between levels 4 and 5 to a prac¬ 
tically vertical attitude between levels 7 and 8 . 
The average dip is about 84°. The dip gradually 
steepens northward until at a point about 600 
feet north of the Elkton shaft the lode is vertical 
and continues so to the Tornado shaft. North 
of the Tornado shaft and south of the Elkton 
shaft the Walter lode becomes less regular and 
is followed with increasing difficulty. On the 
south a series of fissures, ranging in strike from 
north to northeast, which are probably collect¬ 
ively representative of the Walter lode, continue 
into the granite and have influenced the depo¬ 
sition of the Thompson ore. On the north the 
Walter lode finally loses its identity in the ordi¬ 
nary minor Assuring of the country rock. 

Another important lode is the Raven, striking 
N. 20° E. and following the Raven basalt dike. 
The Raven lode and dike join the Walter lode 
between the Elkton and Thompson shafts, the 
dike being generally coincident with the Walter 
fissure zone south of the junction. On the whole 
the Raven dike is about vertical, but it is irregu¬ 
lar, and, like most dikes of its kind in the district, 
often pinches and is replaced by another dike a few feet to one side. It is a narrow 


PHONOLITE 


Co/7t&c£" 


D / \ 

GRANITE Thompson shaft 


Scale of feet 

ZOO 400 


600 


Fig. 34. —Plan showing principal dikes and fis¬ 
sures on level 7 of the Elkton mine. 
































GEOLOGICAL SURVEY PROFESSIONAL PAPER NO. 54 PL. XXIII 



ELKTON MINE AND SOUTH SLOPE OF RAVEN HILL. 





















MINES OF RAVEN AND GUYOT HILLS. 


333 


zone of dikes rather than a single continuous dike. The junction of the dike with 
the Walter lode occurs at distances varying from 350 to 850 feet north of the Elkton 
shaft. In general the junction is farther north on the lower than on the upper levels. 
The general relation of the Walter and Raven lodes may be seen in fig. 34. 

South of the Elkton shaft the Walter lode and the accompanying Raven or 
Elkton dike become irregular and are less readily followed. The narrow fissure 
zone known to the north as the Walter vein here widens to a zone of intersecting 
and individually nonpersistent fissures at least 150 feet in width, as may be well 
seen on level 7 (fig. 34). Attempts have been made to identify one or more of 
these fissures with the Walter vein, but with little success. It seems more reason¬ 



able to conclude that, owing to certain geological relations presently to be described, 
the same forces which farther north produced the well-defined and regular Walter 
sheeted zone here produced a much wider zone of less regular Assuring, no single 
fissure of which can be selected as being alone the equivalent of the Walter lode. 

A third interesting fissure is the so-called Dead vein, an unproductive fault 
lying just north of the Thompson shaft. The Dead vein, or Thompson fault, as 
it may more appropriately be called, strikes N. 72° W. and dips 83° S. On level 
4 it passes about 100 feet north-northeast of the Thompson shaft, and has been 
followed for 80 feet in a drift. It is well exposed also on levels 5, 6, and 7 and 
shown to be a regular and persistent fault which is later than the Walter lode, slightly 
offsetting the basalt dike and the north-south fissure zone on all levels. It will be 
further described in the following section: 

GEOLOGICAL FEATURES. 

The prevailing country rock of the Elkton mine is breccia of the same general 
character as that exposed over the western half of Raven Hill. The Thompson 
shaft, however, and the workings immediately adjacent to it are in granite of the 
13001 — No. 54—06 - 23 






































334 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

coarsely porphyritic Pikes Peak type, such as forms Squaw Mountain. North of 
the Thompson the granite-breccia contact runs nearly east-west, while east of the 
shaft it runs nearly north-south. The Thompson shaft is thus situated within a 
local granite promontory which juts northeastward into the breccia. The contact 
is very irregular in detail, but it is clear from its position on successive levels that 
the promontory in general steeply overhangs the breccia. The granite, as a rule, 
shows considerable shattering near the contact, which, however, is usually fairly 
sharp. Fragments of granite are also abundant in the breccia, in many places for 
distances, of more than 300 feet from the contact. 

The Thompson fault, already referred to, is chiefly in the breccia, though 
nowhere, so far as the present workings show, very far from the granite, except 
where the latter turns southward, east of the Thompson shaft. It is in some 
places a simple fissure containing a foot or more of soft slickensided gouge, in 
others two or more narrower parallel fissures filled with similar material. The 
Thompson fault slightly offsets the basalt dike and the north-south fissures of the 
Walter zone. The net displacement is probably not over 100 feet, though no 
actual measurement of the movement could be made with the exposures available 
at the time of visit. The throw is apparently normal. At a few points, as on 
level 4, the Thompson fault locally marks the contact between the granite and 
the breccia. The fault is merely a more conspicuous example of such local faulting 
near the contact as was noted in the Portland mine (p. 435), the fault fissures 
approaching much more nearly to a plane surface than does the adjacent granite- 
breccia contact. 

The breccia occasionally exhibits a banded structure similar to that observed 
in the Portland mine. Such structure may be seen on level 7, about 450 feet 
north of the Elkton shaft. The banding is here about vertical and is produced by 
very distinct and sharp alternations in the relative coarseness of the breccia particles. 
Similar lamination of the breccia occurs on level 6, about 200 feet south of the 
shaft, the structure in this case dipping north at an angle of 40°. As in the Port¬ 
land, this banding seems to be a local feature and passes by indefinite gradations 
into the ordinary breccia . 

Among the recognizable fragments composing the breccia, phonolite undoubt¬ 
edly predominates, both in the Elkton mine and in the Anaconda-Raven tunnel, 
which furnishes a section through Raven Hill. Fragments up to 6 inches in diam¬ 
eter are common, while much larger masses are occasionally found. The alteration 
of the breccia near the ore bodies consists chiefly of the metasomatic development 
of valencianite, quartz, fluorite, and a little sericite, pyrite in sharp minute pyrito- 
liedrons, and apatite in small greenish-white prisms. Carbonates, particularly 
dolomite, which are common in the altered breccia of other mines, are not abundant 
in the Elkton, and in many places seem to be entirely absent. 

The volcanic breccia of the Elkton workings is cut by several irregular intru¬ 
sive masses of phonolite. One of these is the dike of “purplish phonolite” which 
was noted by Cross® in the upper Raven tunnel and which is exposed on the surface 
passing just above the mouth of the tunnel and the Tornado shaft. The same 

a Geology and mining industries of the Cripple Creek district, Colorado: Sixteenth Ann. Rept. U. S. Geol. Survey 
pt. 2, 1895, p. 89. 







MINES OF RAVEN AND GUYOT HILLS. 


335 


dike is seen in the Anaconda-Raven tunnel, just east of the Tornado shaft. It is 
here at least 100 feet in width. It is probably cut also in the north end of the 
Elkton level 5, north of the Tornado shaft, but this point could not be reached 
from the Elkton shaft at the time of visit. On level 7 this dike is probably cut in 
the main Walter drift north of the Tornado shaft and in the Raven drift, but as 
no particular search for it was made at these points at the time of visit, it was not 
noted. A west crosscut, however, 150 feet north of the Tornado shaft, enters a 
mass of phonolite about 100 feet west of the main drift, which is probably this 
same dike. It will be noted that this dike practically marks the northern limit of 
the Walter pay shoot. As the Walter lode enters the dike from the south the 
fissures become more regular and contain no ore. 

A smaller dike of phonolite with a general northwesterly strike is cut by the 
Walter lode about halfway between the Elkton and Tornado shafts, and conse¬ 
quently near the point where the Walter lode and Raven dike diverge. This dike 
was observed on levels 5 and 6 and seems to dip to the northeast. 

Another important body of phonolite is exposed on level 7, about halfway 
between the Elkton and Thompson shafts. The exact outlines of this body can not 
be determined from existing workings, but it apparently has the general form of a 
small sill or laccolith about 200 feet in average diameter and probably not more 
than 20 to 30 feet in thickness. This mass is considerably fissured and shattered, 
and its contact with the inclosing breccia is seldom well defined. Between this 
body of phonolite and the Elkton shaft occur a number of small masses of phonolite, 
but it could not be determined whether they represent somewhat shattered intru¬ 
sions or are merely isolated fragments in the breccia. A number of phonolite dikes 
are cut in the Anaconda-Raven tunnel in its course through Raven Hill. They 
are of the usual type, and no special study was made of them. 

Granite, breccia, and phonolite are all cut by the Raven or Elkton basic dike, 
which ranges from a fraction of an inch up to 6 feet in width. The average width 
is probably about 3 feet. The Raven dike is exposed at a number of points near 
the surface of Raven Hill, in the upper and lower Raven tunnels, in the Anaconda- 
Raven tunnel, and in the main Elkton workings. One of the most interesting fea¬ 
tures of the dike is its sharp change in course from S. 20° W. to south, where it 
joins the Walter lode. The dike is irregular at the turn, splitting and inclosing 
horses of breccia. Another notable characteristic is the manner in which the dike, 
after being followed for perhaps several hundred feet, gradually becomes narrower 
and finally disappears, though one or more fissures usually continue on beyond the 
point of disappearance of the basalt. Crosscuts into the walls at the point of dis¬ 
appearance usually result in the recovery of the dike, or, rather, of another dike 
belonging to the Raven dike zone. This behavior is well shown in the Anaconda- 
Raven tunnel, particularly where the dike, as it is followed southward, cuts the 
Tornado phonolite dike. After penetrating the phonolite for a few feet the dike 
pinches out. About 40 feet to the west another dike is cut, which also pinches out 
in the phonolite about 100 feet south of the point where the first dike disappeared. 
About 30 feet west of this dike is a third, which continues southward as the main 
Raven dike. A similar behavior may be noted on level 7 of the Elkton, between 
the Elkton and Thompson shafts. The Raven dike, at a point about 75 feet south 


336 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


of the Elkton shaft, turns rather sharply to the south-southwest and soon pinches 
out. Fifty feet farther west another basalt dike is cut, which continues southward 
through the western edge of the plionolite laccolith and into the granite near the 
Thompson shaft. Many other examples might be cited illustrative of this tend¬ 
ency of the Raven-Elkton dike, but it is a feature so characteristic of the basaltic 
dikes of the district as to render unnecessary detailed reference to each case. 

Although portions of the dike are hard and fairly fresh, it is usually rather soft 
and decomposed and breaks up upon exposure to the air. As a rule it is traversed 
by numerous fine cracks, generally parallel with the plane of the dike and particu¬ 
larly abundant near the walls. As in the Portland, some of these cracks are filled 
with veinlets of calcite. In general, however, this platy structure of the dike is 
much less conspicuous than the sheeting of the adjacent breccia. It has less the 
appearance of sheeting produced by external stresses than of originally incipient 
cracks due to the cooling of the basaltic magma and rendered visible by later alter¬ 
ation. This contrast, as well as the way in which the Raven dike turns and fol¬ 
lows the Walter sheeting zone, strongly suggests that the main sheeting of the 
breccia, granite, and plionolite occurred before the intrusion of the basalt, though, 
as will presently be shown, the mineralization is certainly mainly post-basaltic. 
This was clearly the conclusion reached by Penrose/' who writes: 

In fact the dike seems to have been originally intruded into a much-fissured zone and to have come up 
along slightly different lines even in local areas. In several places, also, it forks and follows two diverging 
fissures, though one branch usually comes quickly to an end. The zone of Assuring occupied by the dike and 
that occupied by the [Raven] vein represent different lines of fracture and cross each other at low angles; 
but both fissures were formed before the intrusion of the dike, as is shown by the fact that at the crossing of 
the fissures near the Raven shaft the dike throws out a fork for a few feet from the main dike along the vein 
fissure, thus clearly proving its later age. 

The so-called Catherine dike, noted by Penrose 6 on level 1 of the Elkton and 
supposed by him to be older than the Raven dike, could not be found on the levels 
now accessible and was probably merely a local offshoot from the Raven dike 
along the sheeted zone of the Walter lode. 

FORM AND STRUCTURE OF THE ORE BODIES. 

The important Elkton ore bodies fall into three general classes—first, distinct 
lodes, following either the “basalt” dike or well-defined sheeted zones; second, 
irregular bodies in granite largely due to metasomatic replacement; and, third, 
the peculiar “flat” ore bodies on level 7 between the Elkton and Thompson shafts. 

The main Walter pay shoot has a maximum length of about 1,700 feet and 
with the exception of a few low-grade portions has been stuped continuously from 
the Elkton to the Tornado shaft and from level 7 to the surface. North of the 
Tornado shaft relatively little ore has been found, the north end of the main Walter 
pay shoot practically coinciding with the southwest contact of the Tornado phono- 
lite dike. From the collar of the Elkton shaft the southern limit of the Walter ore 
body pitches south to a point on level 4 about 350 feet south of the shaft. It 
thence pitches north until, on level 7, the south end of the Walter pay shoot proper 
is again at the Elkton shaft. There are, however, below level 6 isolated pay shoots 


a Sixteenth Ann. Rept. U. S. Geol. Survey, pt. 2, 1895, pp. 181-182. 


b Op. cit., p. 185. 







MINES OF RAVEN AND GUYOT HILLS. 


337 


between the Elkton and Thompson shafts on various members of the broad fissure 
zone, which here seems to represent the Walter lode. 

The best ore of the Walter lode occurs along the portion of the fissure zone 
that is accompanied by the Raven dike. North of the point where the dike, turn¬ 
ing olf to the northeast, is known as the Raven vein the Walter pay shoot usually 
contains ore of somewhat lower grade than between this branching point and the 
Elkton shaft. The richest of the Walter stopes thus far worked are said to have 
been between levels 5 and 6. The width of the stopes ranges from 3 to 15 feet, 
the widest stope seen on the Walter lode being on level 5, where the lode crosses 
the small phonolite dike about halfway between the Elkton and Tornado shafts. 
Where the dike is present the ore usually occurs in the small parallel fissures in 
the basalt, which are practically abundant near the walls. It is not restricted to 
these, however, some of the small irregular fissures in the middle portion of the 
dike being sufficiently mineralized to allow of the whole of the dike being stoped 
as ore. The portions of the dike containing ore are usually abundantly impreg¬ 
nated with small crystals of pyrite, this pyritic mineralization being so character¬ 
istic that it is used as an indication of good ore. In many instances, however, the 
calaverite or sylvanite occur with quartz, fluorite, and dolomite in minute veinlets 
in the basalt, the rock between the veinlets exhibiting very little pyritic minerali¬ 
zation. One of this character was seen in a stope above level 6, near the point 
where the basalt and the Walter lode separate. The ore is not always confined to 
the basalt, but sometimes extends for 6 or 7 feet into the breccia on either side, as 
was seen in a stope between levels 7 and 8, south of the Elkton shaft. Here the 
breccia on the east side of the dike shows abundant fine pyrite disseminated through 
it. It has been locally shattered, the interstices between the fragments now con¬ 
stituting little vuggy cavities lined with small crystals of adularia, quartz, fluorite, 
pyrite, and probably sylvanite or calaverite, though the tellurides are not as a rule 
distinctly visible. There are no definite walls to this ore. It passes gradually into 
the country breccia. On level 7, 350 feet south of the Elkton shaft, the east wall 
of the basalt dike, here a part of the phonolite laccolith already described, is also 
locally brecciated and mineralized with pyrite. In this case, however, the pyrite 
is accompanied by visible crystals of sylvanite in the drusy cavities of the rock. 

North of the junction with the basalt dike the Walter lode is a sheeted zone in 
breccia. The average stoping width is about 4 feet, though the zone of distinct 
sheeting is in many places only about a foot wide. The ore, however, is not con¬ 
fined to the regular fissures of the nearly vertical sheeted zone, but extends for 
varying distances into the less regular fractures of the breccia on each side. In 
other words, the lode has no walls. The unoxidized ore occurs exclusively in the 
small vuggy veinlets in and near the sheeted zone as crystals of calaverite or syl¬ 
vanite associated with quartz, fluorite, and in some cases calcite or dolomite. 
More or less pyrite always accompanies tne tellurides. 

Bodies of ore were formerly stoped in the Raven tunnels along the ‘‘basalt” 
dike, but nothing could be seen of these ore bodies in 1903, and the Raven dike 
has not proved productive in the Elkton workings proper, except where it coin- 


338 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

cides with the Walter lode. According to Penrose® the Raven vein is a sheeted 
zone which crosses the dike at a very small angle. The ore is described as occur¬ 
ring in the sheeted zone and also in the dike where the two coincide. 

The granitic ore of the Thompson mine occurs in very irregular masses, gen¬ 
erally similar to those described in the Ajax and Portland mines. These ore bodies 
are related to fissures and occur mainly on the east side of the basic dike, partic¬ 
ularly where two or more fissures intersect (fig. 36). The dike is small and irreg¬ 
ular in the Thompson ground and is not uniformly present, being at some points 
represented by a mere crack in the granite. The main fissures run approximately 
north and south, and probably correspond to the sheeted zone known farther 
north as the Walter lode. There are also a number of fissures on the east side of 
the basalt dike, which strike about N. 35° W., and a few fissures of northeasterly 
strike. The ore is not confined, as in the breccia, to the actual fissures, but extends 
out very irregularly into the granite, which is locally altered to a porous mass, 

containing much secondary feldspar and quartz, 
together with fluorite and pyrite. This metaso- 
matically altered porous granite constitutes the 
ore, which probably owes its value to the occur¬ 
rence of minute crystals of sylvanite or calaveritc 
in the small drusy cavities with which the rock is 
honeycombed. The tellurides, however, are rarely 
visible. 

Between the Elkton and Thompson shafts, on 
level 7, are two so-called flat ore bodies of some¬ 
what unusual type. The larger of these, which is 
almost midway between the two shafts, while irreg¬ 
ular in detail, is of generally oval plan and corres¬ 
ponds ver} T nearly to the plan of the small pliono- 
lite laccolith in which the ore occurs. Near its 

Fig. 3 G.-Pian of ore body in granite, Elkton western edge this phonolite is cut by the Elkton 
mine, level 4 , showing relation of ore to (Raven) basic dike. Near its eastern edge it is 

rlilrG qtiH fiQQiirpQ 

cut by a zone of fissuring commonly supposed to 
be the Walter lode. The ore occurs chiefly between these two north-south lines, 
which are about 120 feet apart. As the north-south fissures, which collectively 
represent the narrower sheeted zone of the Walter lode as known farther north, 
enter the northern edge of the phonolite mass they become very irregular, split 
up, and in part pass into nearly horizontal fissures. One set of such nearly hori¬ 
zontal fissures lying a few feet above level 7 constitutes a fairly definite sheeted 
zone within the phonolite, and is called the “flat vein.” The bulk of the ore occurs 
along this nearly horizontal sheeted zone, but is very irregular in thickness and 
frequently extends for varying distances above or below it along nearly vertical 
fissures. The ore in the “flat vein” proper, however, apparently averages about 
6 feet in thickness and is of relatively low grade. The most interesting peculiarity 
of this ore body is the fact that the ore is practically confined to the much-fissured 
mass of phonolite, nowhere extending for more than a few feet into the surround¬ 
ing breccia except along the Elkton dike to the south and along the main eastern 



a Sixteenth Ann. Rept. U. S. Geol. Survey, pt. 2, 1895, pp. 181-183. 













MINES OF HAVEN AND GUYOT HILLS. 


339 


sheeted zone to the north. The ore minerals (probably svlvanite and calaverite, 
though these are not usually visible) occur in minute veinlets and in little vugs, 
containing quartz, fluorite, roscoelite, and pyrite, at the intersections of minute 
irregular fractures in the phonolite, which is itself impregnated with pyrite. 

The second “flat” ore body lies about 100 feet southeast of the Elkton shaft 
and is smaller than the one just described, extending eastward from the Walter 
lode for a distance of about 50 feet. It is a local expansion of the ore from the 
main lode along a set of probably not very persistent fissures which dip into the 
latter from the east at a low angle. The ore v r as associated with large open cavities 
lined with crystals of fluorite and quartz and containing loose masses of phonolite 
and breccia coated and in places partly cemented together by the same minerals. 
When first opened these cavities were found to be full of water, which is said to 
have flowed out in such volume as to flood the level in about an hour. It is not 
clear whether there was originally a small intrusive mass of phonolite at this point, 
but a portion of the country rock is certainly breccia. There appears to have been 
considerable local shattering, with probably a removal of some of the finer shat¬ 
tered material in solution by the abundant water which deposited the quartz and 
fluorite in the cavities so formed. As all of the ore had been removed at the time 
of visit, the details of its occurrence could not be studied. 

CHARACTER OF ORE. 

The ores of the Elkton mine occur in granite, monchiquite (“basalt”), breccia, 
and phonolite, and consequently exhibit considerable variety. The granitic ore is 
of the same general character as that described in the Ajax and Portland mines, 
but exhibits, if anything, more intense alteration. Much of this ore is exceedingly 
porous, even the original microcline phenocrysts being reduced to spongy skeletons. 
A part of the rock has certainly been removed in solution, while the remainder 
has in some places entirely recrystallized as a carious aggregate of adularia, quartz, 
fluorite, pyrite, and some calaverite, though the last is rarely visible. 

Under the microscope it is seen that the clear secondary feldspar is in many 
cases optically continuous with residual kernels of the older turbid microcline. 
Fluorite occurs partly in solid aggregates, but very largely as minute crystals 
disseminated through the partly sericitized microcline. Pyrite in aggregates or in 
small octahedral crystals occurs abundantly in both the original and secondary 
feldspars, showing a noticeable tendency in the older feldspar to develop in the 
vicinity of microscopic fissures. The exceedingly irregular pores or vugs of this 
ore are lined sometimes with quartz, sometimes with adularia, sometimes with 
fluorite, but more commonly with all three minerals, together with pyrite. Some 
of the pyrite as seen under the microscope is intimately associated with small 
quantities of an obscure opaque material, gray in incident light, which is probably 
molybdenite. 

Fluorite varies greatly in abundance in different parts of the ore bodies and 
is in some places absent. The average tenor of the granitic ore is about an ounce 
in gold to the ton. 


340 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


The ore in “basalt” presents at least two aspects. In the northern part of 
the mine the mineralized “basalt” is a compact gray rock, containing abundant 
microscopic crystals of pyrite thickly disseminated through it. The gold occurs 
in the form of calaverite in little veinlets of quartz which are usually a fraction 
of an inch in width and occur most abundantly near the walls of the dike. Some 
of these veinlets contain druses of fluorite, dolomite, and celestite, as well as quartz. 
In the southern part of the mine the altered “basalt” is light gray and has a porous 
texture, and the crystals of pyrite are larger. The rock contains numerous little 
cavities of dissolution lined with adularia and pyrite. The gold probably occurs 
with the pyrite as calaverite, but this mineral is rarely visible. 

Under the microscope this porous gra} T ore is seen to be an aggregate of adularia, 
sericite, apatite, and pyrite, with probably some calaverite. The sericite occurs 
in exceedingly minute form and its identification is not entirely satisfactory. The 
apatite, which is remarkably abundant, is in slender greenish-white prisms distinct 
in habit and appearance from the stout prisms of smoky apatite that occur in the 
latite-phonolite. The pyrite is chiefly in small pyritohedrons, which are sometimes 
clustered into aggregates. 

The ore found in the volcanic breccia also exhibits two varieties similar to 
those shown by the basaltic ore. In the northern part of the mine, in the Walter 
vein, the ore occurs as calaverite in the usual little quartz-fluorite veinlets of a 
sheeted zone in pyritized breccia. The calaverite is usually most abundant in 
the open vuggy portions of the veinlets and often associated with little hollow 
quartz pseudomorphs after celestite. In the southern part of the mine most of 
the ore in the breccia is found near the basalt dike. Much of this ore has an open 
cavernous structure, apparently due to the removal by solution of some of the 
finer interstitial material of the breccia. The remaining fragments are coated and 
cemented together by drusy incrustations of quartz and pyrite, with locally a 
little fluorite. Associated with these minerals, sometimes in crystals of visible 
size, occur calaverite, sylvanite, and molybdenite. The breccia fragments them¬ 
selves are more or less porous and contain irregular cavities of dissolution lined 
with quartz, pyrite, tellurides, and molybdenite. They also contain disseminated 
pyrite. In some places in the southern part of the mine, particularly in the first 
“flat stope” south of the shaft on level 7, fluorite is very abundant not only incrust- 
ing the fragments of the breccia, but often cementing it into a solid mass. Some 
of the fragments of breccia inclosed in the granular fluorite are rounded and embayed 
and appear to have been partially replaced by the fluorite. It is probable, how¬ 
ever, that their angles received a preliminary rounding by solution before the 
deposition of the flourspar. The microscope shows that between the fluorite 
and the phonolite fragments of the breccia there is usually an intervening zone 
of quartz and adularia. These two minerals have formed by metasomatic replace¬ 
ment of the breccia. 

Another variety of breccia ore occurring in the same flat stope consists of a 
dark-gray spongy mass, looking much like a frothy slag, which fills the interstices 
between masses of shattered breccia. The microscope shows that this porous 
crystalline material consists chiefly of adularia, pyrite, and an obscure opaque 
mineral, bluish gray in incident light, which is intimately associated with the 


MINES OF RAVEN AND GUYOT HILLS. 


341 


pvrite and is probably molybdenite. Within the thicker portions of some of the 
irregular sdpta of the sponge-like mass of residual particles of phonolitic breccia 
not transformed to adularia. Probably some calaverite or sylvanite is present, 
but it is not microscopically distinguishable from the pyrite. Quartz seems to 
be entirely absent, except in the form of little hollow pseudomorphs after celestite 
in some of the open pores of vugs. This material is a local metasomatic alteration 
of the breccia along zones of Assuring and shattering, the spongy mass passing 
, gradually into breccia in which fragments of phonolite are still recognizable. 

The occurrence of phonolite ore is best illustrated in the flat stopes on level 7. 
This ore is a light-gray rock abundantly speckled with minute crystals of pyrite 
and flecked with purple fluorite. It is characterized by a rather porous texture, 
due mainly to the existence of small very irregular spaces of dissolution. The 
origin of these cavities is not always clear. In many instances, however, they 
are enlargements of minute fissures and particularly of several fissures at points 
of intersection. In other cases they are probably due to the removal of ampliibole 
or pyroxene plienocrysts and the subsequent irregular enlargement of the cavity. 
Occasionally these spaces are entirely filled with fluorite. More often, however, 
they are only partly filled with projecting crystals of fluorite, quartz, pyrite, and 
probably calaverite, though the last-named mineral can scarcely ever be distin¬ 
guished by the eye from the bright crystals of pyrite abundant in these little vugs. 

Under the microscope, although small crystals of pyrite are abundantly dis¬ 
seminated through the rock, and though the original pyroxene or ampliibole phe- 
nocrysts have been replaced by fluorite and pyrite, the feldspathic portion of the 
phonolite shows remarkably little alteration. 

Very little oxidized ore is now seen in the Elkton mine. In the Thompson 
workings the granitic ore is more or less oxidized to a depth of about 300 feet. 
No particular difference in value has been noticed between the oxidized and unoxi¬ 
dized ore. Generally throughout the mine there is very little oxidation below the 
300-foot level. 

UNDERGROUND WATER. 

The occurrence and behavior of the underground water of the Elkton mine 
have been fully described in the section devoted to the underground water of the 
district. (See p. 242.) It has been one of the wet mines and the history of its 
water is closely connected with that of the Standard and El Paso tunnels. 

MOOSE MINE. 

INTRODUCTION. 

The Moose mine is situated on the southeast slope of Raven Hill, about half 
a mile northeast of Elkton. The mine is owned by the Moose Gold Mining Company, 
incorporated in 1893, with a capital of $1,200,000. The company owns the Moose 
claim and leases portions of adjoining claims, including the Bertha B. and Kentucky 
Belle. The Trilby mine, also owned by this company, is elsewhere described. 

The Moose was one of the first mines in the district to become productive, 
and up to the end of 1896 made steady shipments of rich ore, the average value 
for considerable periods being nearly $140 per ton. In 1897, however, the ore shoot, 


342 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


which did not extend for more than 400 feet below the surface, was exhausted 
and the mine was closed. It was subsequently reopened and in spite of serious 
difficulties due to water and copious flow of gas into the workings, exploration 
was continued with great persistency in an endeavor to find deeper ore bodies. 
Early in 1904, however, the search was abandoned and the mine is now idle. 

PRODUCTION. 

The Moose mine has produced about 5,100 tons of ore of a gross value of 
$525,000, or an average value of nearly $103 per ton. The dividends paid by the 
company amount to about $144,000. 

UNDERGROUND DEVELOPMENT. 

The Moose shaft, a steep incline with collar 10,117.96 feet above sea level, is 
1,050 feet deep. It connects with 15 levels at various distances apart. The main 
drifts run nearly north and south and explore the Moose basalt dike for a maximum 
distance of about 2,000 feet. Level 6, 350 feet below the collar of the shaft, extends 
farthest south, being prolonged to the surface as an adit, of which the portal is 
1,200 feet south of the Moose shaft. Level 15 (fig. 37) has the greatest northward 
extension, having been driven beneath the old workings of the Bertha B. mine. 
The country rock on each side of the dike has been explored bj" crosscutting and 
diamond drilling. There are two winzes below level 15, one of 60 feet about 450 
feet north of the shaft and one of 20 feet in the Bertha B. ground. 

GEOLOGICAL FEATURES. 

The general country rock of the Moose mine is breccia of the usual Raven Hill 
type. This is cut by a dike of phonolite of general north-south trend and by the 
Moose “basalt” dike. The latter exhibits the usual tendency of these dikes to 
branch or to pinch out and reappear a few feet away in one wall or the other of 
the particular branch first followed out. The general strike of the basic .dike is 10° 
15° west of north, so that it crosses the phonolite dike. The actual crossing could 
not be seen, but the “basalt” is undoubtedly later in age than the phonolite. The 
general relation of the two dikes, as well as the frequent compound character of the 
basaltic dike, is shown in fig. 37, which is a geological plan of level 15. The phonolite 
dike is usually 10 or 12 feet wide, and is fairly regular and persistent. It is in some 
places aphanitic, in others porphyritic in texture, the latter being particularly the 
case in the southern part of level 6. The dike is practically vertical. The “basalt ” 
dike is usually from 2 to 3 feet in width. Near the shaft it dips steeply to the east, 
but on the whole is nearly vertical. The most interesting feature of the breccia is 
the pronounced local Assuring and shattering that it has undergone, particularly on 
the lower levels north of the shaft. This is well shown on level 15, where, from a 
point 128 feet north of the shaft, the breccia for a distance of 650 feet north is a 
porous mass of partially coherent angular fragments, resembling the material 
described in the Conundrum, Moon-Anchor, and Midget mines. This shattering is 
said to extend for about 400 feet above level 15, but the levels in which it is exposed 
were so filled with gas at the time of visit as to be inaccessible. On level 13 this 


MINES OF RAVEN AND UUYOT HILLS. 


343 


shattered rock was described by Superintendent Bush as passing into breccia showing 
very conspicuous sheeting parallel with the walls of the basalt dike. Some of the 
fissures of this sheeted zone were so open as to admit a man’s arm. A little sylvanite 
or calaverite was found on the faces of these slabs, associated with fluorite. The 
breccia was clearly indurated, shattered, and to some extent recemented before the 
intrusion of the “basalt,” which shows only the usual platy parting or sheeting 
parallel with its walls. The eruptive contact of the “basalt” is well shown in 
winzes below level 15, and in one or two cases the interstices between the fragments 
of shattered breccia were observed near the dike 
to be filled with basaltic glass or pitchstone. 

Throughout the mine the rocks exhibit a domi¬ 
nant north-south vertical sheeting. 

» 

LODE SYSTEMS. 

The only lode of importance in the Moose 
mine is the basic dike, already described. In 
the northern part of level 15 a sheeted zone in 
breccia, striking about X. 20° E., has been fol¬ 
lowed toward the Kentucky Belle mine, but no 
ore has been found. 

CHARACTER OF ORE. 

The ore which made the Moose one of the 
best-known mines in the early history of the 
district occurred above level 6 and within 300 
feet of the surface (fig. 38). It was for the most 
part oxidized, consisting of dull gold in minute 
irregular fractures in the basic dike. Calaverite 
was occasionally found, and was evidently the 
form in which the gold was deposited prior to 
oxidation. Specimens of this ore preserved in 
the office of the mine show more or less greenish 
emmonsite (?) and earthy tellurite associated 
with the gold. According to Mr. Philip Argali, 

Some of the Moose Ore cont ained as much as 25 Fig. 37 .—Plan of level 15 of the Moose mine, show- 

. , ing relation of phonolite and basic dikes. 

ounces of silver per ton, the average being 

about 1 ounce of silver to 2 ounces of gold. It is not known in what form this 
metal occurred, but it was probably in tetrahedrite. The deeper levels of the 
mine have shown occasionally a little calaverite associated with fluorite in fissures 
in the basalt dike and in the neighboring breccia. In the winzes below level 15 little 
veinlets of tetrahedrite, galena, and sphalerite, associated with quartz, fluorite, and 
dolomite or calcite, were noted at the time of visit. These little veinlets occur in 
the “basalt” or at the contact between the “basalt” and the breccia, and are usually 
less than a quarter of an inch in width, the ore minerals occurring in their medial 
portions. Some of the cavities and small fissures in the shattered breccia near the 
dike are lined with a drusy aggregate of quartz, fluorite, dolomite, pyrite, and 













344 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


molybdenite. Sylvanite or calaverite occurs sporadically in the dike to the bottom 
of the mine. 

PAY SHOOTS AND LODE STRUCTURE. 

The ore of the Moose mine all occurred in the basalt dike, principally in two 
pay shoots separated by about 100 feet of barren ground. One of these pay shoots 
was at the shaft, the other south of it. The northern body extended from the surface 
nearly to level 6, or to a depth of about 300 feet. It attained its maximum length 
of 160 feet on level 5. The southern pay shoot extended from level 2 to level 5, 
having a vertical range of about 175 feet. Its greatest length, 200 feet, was attained 
between levels 3 and 4 (fig. 38). There was also a small pay shoot north of the 



shaft, between levels 6 and 7. Below level 7, which is 380 feet below the collar of 
the shaft, no body of workable ore has been found. The old stopes are abandoned 
and not safely accessible, so that it is not practicable to study the occurrence of the 
ore. Specimens show, however, that much of it occurred in minute, very irregular 
fissures in the basalt. The latter was altered in the vicinity of the ore to a light- 
gray, aphanitic, almost jaspery mass, probably through the introduction of silica. 
So far as known, the localization of the ore in pay shoots was not determined by 
cross fissures. 



























MINES OF RAVEN AND GUYOT HILLS. 


345 


UNDERGROUND WATER. 

Early in 1896 water was encountered at a depth of about 650 feet, or 9,467 feet 
above sea. The water, however, has been drained away by the drainage tunnels 
and by deep mines at lower altitude, so that the Moose is now dry. 


GAS. 

A heavy gas is exceedingly troublesome in the Moose mine. Its behavior is 
described on page 260. 

JOE DANDY MINE. 

This privately owned mine is situated near the summit of Raven Hill, at an 
elevation of about 10,400 feet. The developments comprise two shafts, each with 
five levels and about 270 feet apart. The southern or main shaft is 580 feet deep, 
and the elevation of the collar is 10,370 feet. Drifts and crosscuts aggregate about 
5,000 feet in length. The production is not known, but must have been fairly 
large. The mine was closed in 1903 and 1904. 

A north-south phonolite dike about 12 feet wide runs just east of the shaft 
house, cutting through the volcanic breccia which forms the country rock. The 
ore occurs chiefly in this dike, which is sheeted and contains disseminated pyrite; 
tellurides occur in the fractures. The dike dips steeply to the east. 

Level 1, which is 180 feet deep, shows a fissure zone which lies 80 feet west 
of the dike in breccia. This zone has been extensively stoped. Large irregular 
bodies of ore have also been stoped in the fissured breccia between this zone and 
the phonolite dike. The ore occurred in seams with fluorite in this mineralized 
rock. 

These two veins—that is, the mineralized phonolite dike and the western 
fissure zone in breccia—come together about 140 feet below the first level, the 
western vein having the flatter dip to the east. They are also said to converge 
in strike so as to join near the road north of the Joe Dandy shaft. On the whole, 
the stoped areas form a shoot continuous at least to the 480-foot level, dipping 
about 70° S. on the plane of the vein and having a maximum horizontal length of 
200 feet. 

NEW HAVEN MINE. 

Just east of the Joe Dandy mine on Raven Hill is the Eclipse No. 1 claim, 
which is owned by the New Haven Gold Mining Company. The production up to 
January 1, 1900, is given as $4,000, but a considerable amount of ore has been 
taken out since that time. The workings consist of an old incline shaft 135 feet 
deep and a vertical shaft 300 feet deep, 150 feet south-southwest of the incline. 
From these shafts about 1,500 feet of drifting and crosscutting has been done. 

The workings are entirely in dense breccia, usually but little oxidized. A 
phonolite dike 50 feet west of the vertical shaft corresponds in position to the 
Joe Dandy dike. It appears to be faulted by a fissure striking N. 55° E. and 
dipping 50° NW. The direction and amount of displacement are not shown. This 
fissure is one of a svstem of parallel fissures or joints. Another system runs N. 
10° E. and dips about 75° E. These two sets of fractures are well defined along a 


346 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


zone 20 to 30 feet wide, 20 to 25 feet high, and about 200 feet long, parallel to the 
north-south fissure system. The vertical shaft is near the eastern side of this zone. 
Within this area the rock is cut into a series of more or less regular blocks, but 
at the margins of the zone the fissures become narrower and less distinct till at last 
they can not be traced at all. Neither system appears to fault the other. The 
levels from the vertical shaft below the first or 130-foot are not extensive nor 
important. 

The workings from the incline shaft expose three definite groups of fissures 
corresponding to those which strike N. 55° E. and dip 50° NW. Each group con¬ 
sists of a series of approximately parallel fractures at small but varying distances 
apart, forming a vein from a few inches to 2 or 3 feet in width. The incline shaft 
is sunk on one of these. A second one occurs about 20 feet southeast of the shaft 
on level 1. It is about 12 feet from the other vein on level 2, showing that the 
two approach with depth, and on the third or bottom level the two are probably 
united to form one, for the second is not seen. The third vein is shown only 
on level 3, where it is 70 feet southeast of the vein on which the incline is sunk. 
It is drifted onto the southwest and connects by a 20-foot winze with the first or 
130-foot level of the vertical shaft. 

The vein on which the incline shaft is sunk carries no ore. The vein just to 
the southeast of it, however, is stoped from the surface down to the first or 38-foot 
level, 3 to 4 feet wide and 60 feet long. Although the vein is oxidized at the sur¬ 
face, tellurides soon appear with increasing depth, and from level 1 down oxidation 
is very slight. The values occur in the narrow seams which collectively make up 
the vein. The Assuring and consequent distribution of the values in this vein 
were sufficient to permit shipping of all the materials broken from the vein. 

The shoot narrows in going down, the stope being 20 feet wide just below 
level 1 and 10 feet at the second or 72-foot level, below which the values were too 
low to make mining profitable. There is no indication of the presence of cross 
seams in this ore shoot. 

On level 3 of the incline the third vein, 70 feet southeast of the shaft vein, 
carries an ore body which has been stoped 4 to 6 feet wide and 15 to 30 feet long 
25 feet above and 35 feet below the level. The ore is similar to that in the vein 
above. No cross seams of importance were observed. 

Level 1 of the vertical shaft explores the area affected by the two series of 
fissures already described. Here ore was encountered. It consisted mainly of 
tellurides contained in the main fissures and the many parallel small seams. The 
rock itself carried very little gold, and hence only the screenings were shipped, 
giving returns of 3 to 5 ounces. When one series of fissures got beyond the influ¬ 
ence of the other system, the values suddenly decreased and soon gave out altogether. 
The shaft is about in the center of a stope which is 60 feet long, 10 feet wide, and 
extends above the level for 30 feet and below for 20 feet. A similar stope, 30 by 
20 feet and 25 feet high, begins 50 feet south of the shaft. One hundered feet 
north of the shaft a chamber 20 by 20 by 20 feet has been made. The values did not 
warrant further stoping at these places, and development is in progress. 


MINES OF RAVEN AND GUYOT HILLS. 


347 


MARY ANN MINE. 

This mine is located near the north end of the Mary Ann claim, near the Joe 
Dandy mine, northeast of the summit of Raven Hill. The property is owned by 
the Mary Ann Mining Company. The production could not be learned, but it is 
very small. The development consists of a shaft 275 feet deep and three levels 
representing S00 to 1,000 feet of drifting and crosscutting. Breccia is the only 
rock encountered in the mine. 

The Mary Ann vein as seen on the first level just east of the shaft has a direc¬ 
tion N. 5° E. and dips 75° to 80° E. It is 3 to 4 feet wide, and consists of a series 
of approximately parallel oxidized seams, some of which carry kaolin. Thirty feet 
south of the shaft it is cut by an oxidized flat vein striking N. 30° W. and dipping 
about 35° NE. It is a much-sheeted, considerabty oxidized zone, 8 to 12 inches 
wide. Along the intersection of these two veins a stope 15 feet long and 5 feet 
wide has been carried up for 25 feet on $30 ore holding rusty gold. A drift along 
the flat vein is being pushed to the southeast with the intention of striking the 
crossing of a vein approximately parallel with the Mary Ann vein and farther to 
the east. 

On level 2 the Mary Ann vein is not very well defined. Sixty feet north of 
the shaft it is crossed by a 3-inch vertical oxidized vein, but no ore was found. 
A drift 15 feet to the east along the cross vein reaches a series of partially oxidized 
seams forming a vein 2 feet wide, which runs N. 5° W. and dips 80° W. At this 
point a flat vein also crosses which corresponds in position and direction to the 
ore-carrying flat vein on the level above. At this triple intersection a stope 10 by 
5 by 20 feet high has been worked. 

About 60 feet west of the shaft on level 2 a vertical 2-inch seam striking N. 
75° W. is cut by a flat vein 6 inches wide striking N. 65° E. and dipping 4° NW. 
Both these veins are simply sheared oxidized zones in the breccia. At their junc¬ 
tion a few tons of 2-ounce ore were taken from a stope, mainly above the flat vein, 
15 feet long, 5 feet wide, and 10 feet high. 

MOHAWK BELLE MINE. 

The Mohawk Belle claim is situated at the head of the northern branch of 
Eclipse Gulch, between Bull and Raven hills. The west end of the claim is being 
worked through a shaft 120 feet deep. Three or four hundred feet of drifting and 
crosscutting have been done from the bottom. An east-west vein dipping 70° N. 
is hems: drifted on and has furnished a small bunch of ore at the surface. 

The east end of the claim was worked some years ago and the Lottie vein, 
which was discovered on the Lottie claim, to the south, produced about $100,000. 
The ore was very rich in rusty gold, some shipments being reported to have yielded 
from $3,000 to $13,000 per ton. 

IDA MAY MINE. 

The Ida May property, located on the summit of Raven Hill and consisting of 
the Ida May, Little Clara, and Mountain Girl claims, is owned by the Ida May 
Gold Mining Company. The production up to 1900 was over $40,000. ° There are 


a Hills, Fred, Official Manual of the Cripple Creek District, 1900. 




348 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

three shafts on the property, the deepest attaining 375 feet, with 800 feet of drifting. 
Yen* little work has been done lately. The general country rock is breccia. The 
old shaft, visited by Penrose in 1S94, is about 200 feet deep and the upper level 
only is accessible. A basalt dike 1 foot wide and about vertical runs through the 
shaft with a course N. 5° W. Sixty feet north of the shaft the dike branches, one 
branch curving around to the east until it has a course of about N. 75° E. South 
of the shaft the dike turns N. 35° W., and a phonolite dike appears alongside the 
basalt. This phonolite dike is very small near the shaft, but widens to about 2 
feet at the south face of the drift, about 80 feet south of the shaft. It is intersected 
by the basalt dike. The ore occurred in the basalt, particularly where fissures 
come in from the walls. 

Northeast of the old shaft, near the road, is a new shaft, 400 feet deep, sunk 
by lessees. The basalt dike is here about vertical and is reached by short cross¬ 
cuts from the shaft. The average width of the dike is about 2 feet. It constituted 
an ore body above and a short distance below level 1, the ore occurring in the dike 
itself, usually richest on the west side. The average value of the ore was about 
$15. Tellurides occur in fractures, accompanied in many places by an obscure 
greenish mineral, possibly roscoelite, said to be indicative of good ore. 


CHAPTER IV —MINES OF BEACON HILL. 


GENERAL INTRODUCTION. 

Beacon Hill, like Guyot Hill, is merely a prominent knob on the general south¬ 
west spur of Raven Hill. The principal geological feature of the hill is a vertical plug 
of phonolite, elliptical in plan, which is intrusive into the Pikes Peak granite and has 
been described on page 34. Tliis phonolite forms approximately the upper 150 feet 
of the hill, the lower slopes being granite. There are a number of prospects in the 
phonolite, but the productive mines are all in the granite. They lie in two belts 
parallel to the longer or northeast-southwest axis of the elliptical plug. One of 
these belts is on the northwest side of the hill and includes the El Paso, C. Iv. & N., 
Old Gold, Henry Adney, and other mines and prospects. The other is on the south¬ 
east side of the hill and embraces the Prince Albert, Gold Dollar, Zoe, Mabel M., 
Agnes, and St. Thomas mines. The general relation of the veins to the phonolite 
plug is shown in fig. 40 (p. 351). 

The Beacon Hill mines are noteworthy as lying at a greater distance from the 
main area of breccia than the other productive mines in the district. Their relation 
to the phonolite plug strongly suggests a genetic connection between this intrusion 
and the formation of the veins. 

EL PASO MINE. 

INTRODUCTION. 

The El Paso mine is situated on the northwest slope of Beacon Hill and is owned 
by the El Paso Consolidated Gold Mining Company. The original El Paso com¬ 
pany, organized in 1894, with a capital of $900,000, owned the Orizaba No. 1, 
Orizaba No. 2, Fannie B., Vulcan, and Bryan Fraction claims, covering about 
25 acres. Later the company was reorganized under its present title, with a capital 
of $2,500,000, and the Columbia No. 1, Columbus, Australia, Old Hickory, and 
Little May claims acquired. 

PRODUCTION. 

The gross production of the El Paso mine up to the end of the year 1903 was 
$1,698,576. The production for 1904 (with December conservatively estimated 
by the company) was $1,337,735, making a total of $3,036,311. The dividends 
paid in the same period amount to $506,250, besides which the company has added 
considerabh r to its holdings and has equipped' the mine in a very substantial 
manner. 

UNDERGROUND DEVELOPMENT. 

There are two important shafts on the El Paso property—the old El Paso 
shaft, near the east end of the Orizaba No. 1 claim, and the present main shaft, on 
the Columbia No. 1 claim, 600 feet north of the old shaft. The former is no longer 


13001 — No. 54—06 - 24 


349 


350 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


used. The new shaft is 560 feet deep and the old shaft a little deeper, as it is higher 
up the slope. There are four levels connecting with the main shaft, designated as 
levels 1. 2. 3. and 4 and nm at 190, 310. 440. and 560 feet, respectively, below the 
collar. The general trend of these levels, as well as of the upper drifts from the old 
shaft, is X. 30° E. There are also some important drifts in the northern part of 
the mine, which run generally X. 75° E. Levels 2 and 4 connect with the old shaft, 
and also with two of the great drainage tunnels of the district, level 2 being contin¬ 
uous with the Standard tunnel and level 4 with the El Paso drainage tunnel. 

GEOLOGICAL FEATURES. 

The El Paso workings are in granite on the western side of the Beacon Hill 



Fig. 39.—Plan of level 2 . El Paso mine, showing relation of veins and ore bodies to phonotitic Lot instants. 


somewhat gneissoid. and contains numerous squeezed lenticular bodies of schist, 
which appear in some cases to have been derived from the granite by local shearing 
under great stress. The granite is cut by numerous dikes and sills of phonolite. 
many of which are clearly offshoots from the main phonolite plug. The most 
important dike is one striking about X*. 55° W.. shown in fig. 39. and also on the 
general geological map (PI. II. in pocket . The dike dips from 55° to 60° MV., and 
is usually 15 to 20 feet wide. From its importance in the El Paso mine this dike 
may be conveniently referred to as the El Paso dike. 

The contact between the phonolite plug and the granite is well exposed in the 
Australia tunnel and on levels 2 and 4 from the main shaft. It is a sharp, irregular 













U. S. GEOLOGICAL SURVEY 


PROFESSIONAL PAPER NO. 54 PL. XXIV 



A. MINES ON BEACON HILL. 

The El Paso is high up in the center; the C. K. & N. to left in the middle-ground; the Henry Adney and Old Gold in the middle and 

right foreground, respectively. 



/L BEACON AND GROUSE HILLS, FROM RAVEN HILL. 






















































MINES OF BEACON HILL. 


351 


intrusive contact, along which there has been occasionally a little local movement. 
Sills and dikes of phonolite are particularly abundant in the granite near the main 
phonolite mass, as may be well seen on level 2 and in the east branch of the new 
drainage tunnel. The contact dips steeply into Beacon Hill, usually at 75° or 80°. 
(See fig. 40.) 

LODE SYSTEMS. 

The principal lodes of the El Paso are the El Paso, Tillery, and C. K. & N. The 
El Paso and Tillery strike in general N. 35° E. Both dip northwest, the El Paso 
at about 70° and the Tillery at about 65°. They thus converge downward. At the 

X 

c 

o 

© o 

<0 



Fig. 40 — Diagrammatic northwest-southeast section across Beacon TTill, through El Paso and Zoe shafts. 


surface, near the old shaft, they are approximately 150 feet apart, while in the 
southwest part of level 4 they are apparently together. They diverge, however, to 
the northeast, and at the new shaft are 70 feet apart on level 4. Both lodes are 
rather irregular in strike and dip. The Tillery is very indistinct north of the main 
shaft and has not proved important in that direction. An east crosscut on level 2 
shows that the granite through which the Tillery lode would pass if it persisted so 
far north is too much shattered to allow the identification of the lode. The maxi¬ 
mum explored length of the Tillery lode is about 700 feet, chiefly in the vicinity of 
the old shaft. The El Paso lode has been explored from a point about 450 feet south¬ 
west of the old shaft to a point 800 feet northeast of the new shaft, a total length 
of 1,850 feet. On level 1 the El Paso lode meets the El Paso dike just east of the 
new shaft. The lode follows the foot wall of the dike for about 175 feet, and then 
turns slightly northward across the dike and continues on to the C. K. & X. lode. 
On level 2 the lode and dike exhibit a similar relation, the crossing on this level being 
about 500 feet northeast of the shaft (fig. 43). On levels 3 and 4 the intersection 
occurs successively farther north and nearer the C. K. & X. lode, but the develop¬ 
ment in this part of the mine was not extensive enough at the time of visit to make 
clear all the details of the relation between the dike and the El Paso and C. K. & X. 
lodes. Xear the dike the El Paso lode is rather irregular and changeable in dip 
and may be accompanied by considerable subsidiary Assuring. At the point 





















352 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


where the lode enters the dike from the southeast a zone of Assuring usually branches 
which continues northeast along the foot-wall contact of the dike. This is narrow 
and contains pyrite, but no ore. The C. K. & N. lode has a general strike of N. 75° E., 
but it is a rather curved and irregular zone of Assuring, part of this irregularity 
being due to a number of cross fissures, some ol them having the same general trend 
as the El Paso and Tillery lodes. The dip of the lode varies, but is practically 
vertical. 

The intersection of the El Paso and C. K. & N. lodes has been exposed on all 
four levels, but the exact relation of the two lodes is not decisively shown. On 
level 2 the C. K. & N. lode is offset about 10 feet at the intersection, but it is not 
certain from this that the El Paso is the younger lode.. No corresponding dis¬ 
placement was noted on the other levels. On level 1 the C. K. & N. lode runs 
S. 83° W. for about 150 feet from the El Paso lode, the dip being vertical. The 
lode then turns S. 40° W. along an intersecting fissure zone, and follows this course 
for about 100 feet before resuming its normal strike. This cross-fissure zone dips 75° 
NW. The fissure zone continues beyond the C. K. & N. lode both to the northeast 
and southwest, containing some soft, gray gouge and rather crumbling pyrite. It 
might be regarded as a simple faulting of the C. K. <fe N. lode were it not for the fact 
that the ore of the latter lode continued without change along the faulting or inter¬ 
secting fissures. The same fissure zone appears also on level 2, and has been fol¬ 
lowed for some distance in a drift (fig. 43). On this level, near the C. K. & N. line, 
the C. K. & N. lode is offset by a second cross-fissure zone, striking N. 30° E. This 
fissure zone also dips northwest about 75°. It is similar to the cross lode just 
described, but, unlike that fissure zone, contains no ore, and seems clearly to fault the 
C. K. & N lode. It is a well-defined sheeted zone in the granite, one of the fissures 
near the hanging wall containing a soft, gray gouge of sheared granite, with some 
pyrite. Similar cross fissures, usually containing a little soft gouge and pyrite, 
cross the C. K. & N. lode east of its intersection with the El Paso. They usually 
strike about N. 30° to 35° E. and dip about 75° NW. Some cross the C. K. & N. 
with no apparent displacement of the latter. About 100 feet east of the El Paso 
lode, on level 1, the C. K. & N. lode apparently ends at one of these fissure zones. 
Whether the C. K. & N. is actually faulted or merely terminates at this cross Assuring 
is unknown, as the continuation of the lode has not yet been identified. The same 
cross-fissure zone apparently cuts off the eastern part of the C. K. & N. on level 2, 
about 60 feet east of the El Paso lode. A few feet beyond this point the El Paso 
dike crosses the line of the 0. K. & N. lode (fig. 39, p. 350), which is supposed to 
turn northeast and follow the dike. As there is a difference of only about 20° 
between the normal trend of the lode and the course of the dike, the Assuring 
was probably deflected along the dike contact in preference to taking an oblique 
course through the phonolite. In this part of its course it dips 65° to 70° NW., 
conforming to the usual dip of the dike. This change of dip was observed also at 
the east faces of the drifts on the C. K. & N. lode on levels 3 and 4, as these faces 
were at the time of visit. Developments on levels 3 and 4 had not then reached 
such a stage as to throw much additional light on the relation of the C. K. & N. 
lode to other structural features in the mine. 


MINES OF BEACON HILL. 


353 


From the foregoing description it appears that the El Paso ground is cut by 
a number of fissure zones striking approximately N. 35° E. and dipping 70° to 75° 
NW. To this prevalent system the nearly east-west vertical C. K. & N. lode is a 
marked exception. 

CHARACTER OF ORE. 

The ore of the C. K. & N. lode consists of calaverite, which occurs chiefly in 
the vugs and narrow veinlets of the sheeted zone composing the lode. The calave¬ 
rite is usually associated with quartz and fluorite, and locally with pyrite and sphal¬ 
erite. The pyrite and sphalerite were apparently deposited before the calaverite 
and carry small values, $5 or $6 per ton being about the maximum. Free gold is 
rare in the C. Iv. & N., and the pay shoots contain practically no oxidized ore. 
Some low-grade ore in the C. K. & N. lode on level 4 shows an indistinctly banded 
vuggv aggregate of quartz and purple fluorite. The banding is apparently due to 
the replacement by these minerals of the very thin granitic slabs between the closely 
spaced fissures of the sheeted zone. 

No ore was being taken from the El Paso or Tillery lodes at the time of visit. 
Specimens of Tillery ore from level 1 near the old shaft show the occurrence of both 
calaverite and tetrahedrite, associated with fluorite as implanted crystals on the 
drusv quartz lining the vugs and narrow fissures of the sheeted zone. Some of 
these fissures show a nearly solid filling of quartz and barite, with pyrite and sphal¬ 
erite. These minerals belong to an earlier generation than the calaverite and tetra¬ 
hedrite. None of the ore formerly mined from the El Paso lode near the old shaft 
was seen. The ore of the large pay shoot in this lode northeast of the new shaft 
consisted chiefly of shattered granite containing innumerable reticulating veinlets 
of quartz. These small, irregular fissures are seldom completely filled, but are 
vuggy or merely lined with drusy quartz. The valuable constituent of the ore is 
calaverite, which occurs in the vugs and on the drusy surfaces. Galena, stibnite, 
and chalcopyrite are said to be occasionally present in the ores. 

The value of the El Paso ore ranges from about $8 to several thousand dollars 
per ton. In general $40 or $50 ore is considered good. 

PAY SHOOTS AND LODE STRUCTURE. 

The C. K. & N. lode is a typical sheeted zone in granite. The ore is rarely 
over 7 inches wide and is confined to one or more vuggy quartz veinlets. The ore 
forms practically one continuous shoot, which has been stoped from level 2 to the 
highest point at which pay ore occurs—namely, 100 feet above level 1 and 150 feet 
below the surface. On the east the pay shoot ends above level 1 at the zone of 
northeast Assuring already described, but between levels 1 and 2 it extends about 
125 feet farther along the El Paso dike. Toward the west the pay shoot extends 
into the C. K. & N. mine, the upper limit of the ore pitching down at a somewhat 
steeper angle than the slope of the hill, so that at the C. K. & N. shaft it is about 
200 feet below the surface. The length of the shoot on level 2 within the El Paso 
ground is nearly 800 feet. No stoping had been done on levels 3 and 4 at the time 
of visit, though recent work is reported to have shown large bodies of good ore 




354 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


down to the bottom level. The extreme upper limit of the ore seems to be deter¬ 
mined, at least in part, by a zone of nearly horizontal Assuring containing soft, 
crushed granite or gouge and some pyrite. At those points where the pay shoot 
follows fissures crossing the plane of the C. K. & N. lode it contains ore of the same 
character as in the C. K. & N. lode proper, but this ore is usually accompanied by a 
fissure containing soft gouge and pyrite (fig. 39, p. 350). Such soft material never 
constitutes pay ore. Some of the best ore on the C. K. & N. lode occurs near its 
intersection with the El Paso lode. 

The old stopes on the El Paso lode near the old shaft are no longer worked, and 
no observations could be made on the occurrence of this ore. The pay shoot or 
shoots in this part of the lode appear to have had a total length of about 500 feet 
and come to an end near the new level 1, or approximately 200 feet below the sur¬ 
face. At this depth the lode shows a little oxidation, but only along some of the 
more open fissures of the sheeted zone. On level 2 the El Paso sheeted zone, while 
fairly distinct, contains no ore south of the main shaft. The principal pay shoot in 
this lode lies northeast of the main shaft, chiefly in the acute angle formed by the 
intersection of the lode with the El Paso dike. This ore formed an irregular mass, 
which extended from a point about 70 feet above level 1 almost to level 3. Near 
level 1 the pay shoot is only a few inches wide, and is a sheeted zone in granite at 
the under cont act of the El Paso dike. The ore occurs as calaverite, mainly in the 
medial vugs of a veinlet of fluorite less than an inch wide. Above the level this 
veinlet finally pinches out. Below the level the main fissure diverges from the pho¬ 
nolite, and the granite between it and the dike is much fissured and mineralized, con¬ 
stituting on level 2 an ore body 40 feet wide. The irregularity of the Assuring at this 
point appears to be connected with an irregular sill-like offshoot from the phonolite 
dike into the granite and the presence in the latter rock of some streaks or inclu¬ 
sions of schist. The El Paso lode itself also splits into a number of fairly regular 
divergent sheeted zones as it approaches the under side of the dike. Granite, phono¬ 
lite sill, and schist lenses are all traversed by reticulating fissures containing quartz 
and calaverite. Below level 2 the Assuring becomes less pronounced, the ore con¬ 
tracts, and on level 3 there is practically no ore where the El Paso lode and El Paso 
dike meet. The ore body has, roughly speaking, the form of a flattened ellipsoid 
lying against the under side of the phonolite dike, its longest axis pitching to the 
northeast with the general line of intersection of lode and dike. The ellipsoid has 
its greatest thickness of 40 feet near level 2, about 200 feet northeast of the main 
shaft, and decreases peripherally to zero. It is far from regular, however, as it 
contains several horses of unmineralized country rock, and the ore often extends 
for short distances along some of the more definite fissure zones. 

Although the main contact between the granite and the Beacon Hill phonolite 
plug is not generally mineralized, it carries bodies of ore at several points, notably in 
the now idle workings of the Australia tunnel and Little May mine. In the El 
Paso workings some ore occurs along the contact on level 2, but only in one or more 
irregular sills in the granite, which connect with the main phonolite mass. There 
has been slight movement along the general contact since the phonolite solidified, 
and the sills are irregularly fissured. In one stope visited the sill was about 6 feet 
in thickness and contained ore for a maximum distance of 15 feet from the main 
contact. The ore occurs as calaverite in the minute fissures in the phonolite. 


MINES OE BEACON HILL. 


355 


C. K. & N. AND OLD GOLD MINES. 

INTRODUCTION. 

» * 

The C. Iv. & N. mine adjoins the El Paso on the northwest, with workings on 
that part of the C. K. & N. lode lying within the Raaler claim. It is owned by the 
C. K. & N. Mining Company, of Colorado Springs, incorporated in 1894 and capital¬ 
ized at $1,250,000. The authorized capital was afterwards increased to $1,500,000. 
Very little work was done on the property until the end of 1899, when it was leased 
for five years to Mr. Horace Granfield, the company receiving 20 per cent on the net 
value of the ore. Although the C. K. & N. lode was not then known in the El Paso 
mine and does not show at the surface, Mr. Granfield sank a shaft 300 feet in depth, 
practically on the lode, and discovered ore in the latter part of 1901. The mine 
has since produced steadily and is noted for the high grade of its ore. 

The Old Gold mine lies immediately west of the C. K. & N., the workings 
being connected on the C. K. & N. lode. It is owned by the Old Gold Mining Com¬ 
pany, of Denver, organized in 1895 and capitalized at $1,800,000, subsequently 
increased to $2,101,150. The property comprises isolated portions of the Old Gold, 
Buckeye, Genevieve, and Lonaconing claims not covered by earlier locations. One 
was first discovered in 1903 by the lessee, E. G. Taylor, superintendent of the C. K. 
& N. mine, at a depth of about 300 feet. 

PRODUCTION. 

The output of the C. K. & N. mine is as follows: 


Production of C. K. & N. mine. 


Year. 

Gold. 

Silver. 

1902.:. 

Ounces. 

9,095 
19,390 
32,093 

Ounces. 

(°) 

510 

(“) 

1903. 

1904. 


60,578 

510 


a Silver for this year probably included with the gold. 


The total gross value of the product is $1,211,553, and the company has paid 
from royalties twelve dividends up to December 31, 1904, amounting to $171,828. 

The Old Gold mine produced up to May 1, 1904, 4,984.57 tons of ore, of a gross 
value of $207,412.18. The royalties to the company, on a basis of 15 and 20 per 
cent of the net value of the ore, amounted at the same date to $29,909.65, and the 
first dividend, $10,505.75, or $5 per thousand shares, was declared in March, 1904. 

UNDERGROUND DEVELOPMENT. 

The C. K. & N. is a small mine, with very simple workings along the one lode. 
The main shaft, situated close to the El Paso line, is 498 feet deep and connects with 
three levels, level 1 being 300 feet below the surface, while the other levels are at 
intervals of 75 feet. These levels run diagonally across the Raaler claim, following 

















356 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

the C. K. & N. lode, which strikes N. 76° E. They end on the northeast against the 
El Paso and on the southwest against the Old Gold properties, giving a total stoping 
length along the lode of about 400 feet. The Old Gold shaft, sunk on the C. K. & N. 
lode 400 feet southwest of the C. K. & N.' shaft, is also about 400 feet in depth. 
The main level is 250 feet below the surface, and consists of a drift about 125 feet 
in length along the C. K. & N. lode, with a northeast-southwest drift on the Old 
Geld lode. The bottom level, 80 feet lower, consists of a similar drift on the C. K. & 
N. to the Old Gold lode. The collar of the Old Gold shaft is 98 feet lower than 
that of the C. K. & N. shaft. 

GEOLOGICAL FEATURES. 

« 

The C. K. & N. and Old Gold workings are in the same granite as the El Paso 
mine. This granite is cut by a number of small, irregular sills and dikes of phonolite. 
In the Old Gold ground there is a prominent phonolite sill or dike 30 or 40 feet in 
thickness, which dips to the northwest at about 45°. Thickness and dip, how¬ 
ever, are both variable, and in some places the sill is divided into an upper and lower 
sheet by a slab of schist. Similar schist overlies the phonolite, which apparently 
was intruded along a schistose streak or inclusion in the granite. 

LODE SYSTEMS. 

The principal lode is the C. K. & N., which strikes N. 76° E., and is approxi¬ 
mately vertical. It extends from the El Paso ground across the Raaler claim, and 
into the Old Gold ground until it meets the phonolite sill. Northwest of this sill 
no trace of the C. Iv. & N. lode has yet been found, and it probably does not cross it. 
The Old Gold lode is a nearly vertical fissure zone in the sill, striking, like the latter, 
N. 35° E. It is known only on the 300-foot level of the Old Gold, as it is not dis¬ 
coverable as a distinct lode in the schist and granite above and below the phonolite. 
There are a few small cross fissures in the C. K. & N. mine, striking about N. 30° E., 
and thus, like the Old Gold lode, corresponding to the general system of north¬ 
easterly lodes represented by the Tillery and El Paso veins. They do not perceptibly 
displace the C. Iv. & N. lode. 

CHARACTER OF ORE. 

The ore of the C. Iv. & N. lode consists of calaverite in a gangue of quartz 
associated with varying amounts of fluorite, and, as shown by concentrating at the 
Dorcas mill, with some barite. The calaverite sometimes projects as implanted 
crystals into small quartzose vugs, but probably the greater part of it is completely 
inclosed by the gangue. Occasionally nests of stibnite have been found in the lode, 
carrying up to 300 or 400 ounces of gold per ton. Chemical examination of such 
stibnite by Doctor Hillebrand shows that the gold exists as a telluride, probably 
mechanically included in the stibnite. None of the ore seen showed any sign of 
oxidation, and free gold is unknown. Some of the ore is remarkably rich, small 
quantities carrying as much as 3,000 ounces of gold per ton, while one lot of 1,586 
pounds netted 819,000, corresponding to about 1,200 ounces per ton. The average 
proportion of silver in the ore is 1 ounce to 8 or 10 ounces of gold. Some of the ore 
contains as much as 300 ounces of silver per ton. The ore of the Old Gold lode, 


MINES OF BEACON HILL. 


357 


occurring in fractured phonolite, sometimes shows considerable pvrite, in small 
pyritohedrons lining the little vugs and fissures, and often accompanied by sphal¬ 
erite. 

PAY SHOOTS AND LODE STRUCTURE. 

The principal pay shoot in both mines is that of the C. K. & N. lode, which 
has already been partly described in connection with the El Paso mine. The 
lode is a narrow sheeted zone cutting through granite and phonolite, the ore occur¬ 
ring in both rocks, though it is usually wider in the granite. The fractures are 
partly open, particularly the principal fissure of the zone, and show no gouge or 
slickensiding. The main fissure is rarely more than 4 inches wide. It is some¬ 
times solidly filled with quartz and calaverite, but more often shows an open 
vuggy structure, the calaverite occurring both as implanted crystals in the vugs 
and within the quartz lining the walls of the fissure. Occasionally the main fissure 
contains nearly loose slabs of country rock, a few inches in thickness, coated on 
all sides by crystals of quartz and fluorite. Calaverite occurs also in the smaller 
less regular fractures on each side of the main fissure, as is indicated by the fact 
that the screenings from a width of 3 or 4 feet are usually of high grade. Accord¬ 
ing to Supt. E. G. Taylor, the calaverite (or some other gold telluride) sometimes 
occurs alongside the principal fissure in granite that is not perceptibly fractured. 
Such granitic ore is grayish or greenish in color and somewhat porous, showing 
metasomatic alteration, whereas the unaltered granite is reddish in color and 
dense in texture. This pay shoot has been stoped from the El Paso line into the 
Old Gold ground and from the 370-foot level to within 165 feet of the surface. No 
ore is known above this, though the lode is said to have been followed for about 30 
feet above the point where the ore ended. Toward the west the pay shoot con¬ 
tinues to the Old Gold phonolite sill. In the phonolite the lode splits into a few 
small, irregular fissures and is soon lost. The ore does not extend into the phonolite 
and has been found to fall rather below the average grade as the sill is approached. 
On level 3 of the C. K. & N. no stoping had been done at the time of visit in January, 
1904, and it was a little doubtful whether the C. K. & N. lode had been found. 
The fissure followed in the drift was very indistinct, showing only a little pyritic 
mineralization in granite alongside a small phonolite dike. No calaverite and 
nothing resembling the open, vuggy C. K. & N. lode as known above were seen on 
this level. 

The Old Gold pay shoot was first encountered on level 1 of the Old Gold as a 
small, rather irregular, vuggy fissure in the phonolite sill, accompanied by some 
irregular fracturing. The best ore occurs in the main fissure, but the irregular 
fractured phonolite is also ore to a maximum width of 10 feet. As this ore proved 
to be of high grade and showed such a width on this level, chutes were put in and 
the drift timbered preparatory to carrying up an extensive stope. It was soon 
found, however, that the ore extended only 15 feet above the level, being limited 
to the phonolite. Later developments on the level below have shown also that 
this pay shoot does not extend below the bottom of the phonolite. 


358 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


UNDERGROUND WATER. 

A considerable quantity of water finds its way into the mine through the open 
portions of the C. K. & N. lode and through cross fissures, but is kept down by 
natural drainage into the El Paso mine. By working above the water level main¬ 
tained bj^ its larger neighbor the C. K. & N. mine is able to avoid pumping. 


GAS. 

An abundant flow of gas, in part carbon dioxide, issues from some of the 
fissures of the C. K. & N. lode, so that a candle held to such an opening is imme¬ 
diately extinguished. Owing to the connections with the El Paso and Old Gold 
.shafts, the mine was well ventilated and the gas was causing no particular incon¬ 
venience at the time of visit. 

PRINCE ALBERT, GOLD DOLLAR, ZOE, AND MABEL M. MINES. 

INTRODUCTION. 

The Prince Albert, Gold Dollar, Zoe, and Mabel M. mines "are all situated on 
the southeast side of Beacon Hill, near the contact between the granite and the 
phonolite. The Prince Albert mine includes the Prince Albert, Beacon, and Eureka 
claims and is owned by the Prince Albert Mining Company (Limited), incorporated 
in 1895 with a capital of 83,000,000. It represents a consolidation of the Prince 
Albert, Beacon, and Ida Etheleen companies. Both the Prince Albert and Beacon 
mines began shipping ore in 1893 and attracted much attention to Beacon Hill. 
In 1896 the Prince Albert was shipping 20 tons of $40 ore a day. Most of the 
work in the last few years has been done by lessees. 

The Gold Dollar mine lies immediately northeast of the Prince Albert and 
with the Mabel M. mine is controlled by the Woods Investment Company. The 
Zoe mine occupies a narrow strip of territory between the Gold Dollar and Mabel 
M., with a maximum stoping length along the lode of about 60 feet. The Gold 
Dollar, Zoe, and Mabel M. properties are all portions of the Arequa town site and 
were not laid out as mining claims. The Gold Dollar mine began to ship in 1897 
and the Mabel M. at about the same time. Both are now operated by lessees. 

UNDERGROUND DEVELOPMENT. 

All of the mines lie approximately on a line running N. 35° E., the principal 
drifts having nearly the same trend. The workings of the Prince Albert mine are 
practically all at the northeast end of the property, near the Gold Dollar line. 
They comprise several shafts and adits, some irregular levels, and extensive stopes 
and open cuts. The deepest shaft is 250 feet and most of the workings are within 
100 feet of the surface. Beneath the Prince Albert workings proper the ground 
has been explored at a depth of about 300 feet by the Gold Dollar adit. 

The Gold Dollar shaft is a little over 420 feet in depth, with six levels. Of 
these, level 4, 221 feet below the collar, is the most extensive and connects directly 
with the Gold Dollar adit from Arequa Gulch. The Zoe shaft is an incline, of 
which the bottom level is level 5 of the Gold Dollar. The Mabel M. shaft is about 
475 feet deep, with five main levels. The total length of ground exploited in the 
four mines is about 1,500 feet. 




\ 


MINES OF BEACON HILL. 359 

GEOLOGICAL FEATURES. 

The workings are nearly all in gneissoid granite, near the contact with the 
main phonolite mass of Beacon Hill. In this respect the ^geological conditions are 
similar to those in the El Paso and C. Iv. & N. mines on the other side of the hill. 
The contact between the 
granite and the phonolite 
is very irregular, as may 
be seen from fig. 41. It 
dips, as a rule, steeply into 
the hill, the average angle 
being probably about 75°. 

In places the granite is 
only slightly brecciated 
near the contact. Else- 
where the two massive 
rocks are separated by as 
much as 15 feet of breccia, 
composed of mingled frag¬ 
ments of phonolite and 
granite. There is usually 
much pyrite along the 
contact, impregnating 
both massive and brec¬ 
ciated rocks, but no ore. 

In the open cut and 
stopes in the Prince 
Albert mine bodies of 
similar breccia are in¬ 
closed in the phonolite. 

It is probable that an 
explosive eruption first 
shattered and pierced the 
granite of Beacon Ilill 
and that the phonolite 
magma subsequently rose 
in the volcanic neck al¬ 
ready partly. filled with 
the phonolite and granite 
fragments produced by 
the explosion. In the 
open cut of the Prince 
Albert the phonolite cuts the breccia with'a well-defined intrusive contact. 

The granite is traversed by several irregular dikes and sheets of phonolite, 
some of which are clearly offshoots from the main phonolite neck or stock. 



Fig. 41.—Sketch plan of level 4, Gold Dollar mine, showing relation of fissures to 
the phonolite plug of Beacon Hill. 






360 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT, 

LODE SYSTEMS. 

The granite for a distance of about 200 feet from the main phonolite mass is 
cut by a number of fissures which, for the most part, strike about N. 35° E. This 
strike is roughly parallel with the longer axis of the Beacon Hill phonolite intrusion 
and with the numerous fissures in granite in the El Paso workings on the other side 
of the hill. The individual lodes composing this general fissure zone range in strike 
from N. 10° E. to N. 40° E. They dip usually to the northwest, the angles ranging 
from 60° to 90°. The principal lodes are the Prince Albert, Gold Dollar, Lindsay, 
Mabel M., and Parker & Head. Owing to the irregular and disconnected character 
of the underground workings the mutual relations of these lodes are not clear. It 
is possible, for example, that the Gold Dollar and Lindsay are really parts of one 
lode, but the connections through the Zoe mine are not such as to establish this 
identity. The Gold Dollar lode has a dip of about 70°, while the dip of the Lindsay 
is 60°. In general the fissure zones are not very persistent and where they do not 
contain ore are not always distinguishable from other fissures of similar trend, but 
of no known economic importance. The fissures frequently branch and intersect 
one another, but, so far as known, none of the intersections show faulting. 

The Gold Dollar and Lindsay lodes constitute practically the southeastern 
boundary of the known zone of productive fissures. The other lodes lie between 
these two and the Beacon Hill phonolite and are usually more nearly vertical. 

CHARACTER OF ORE. 

The ore in these mines occurs as calaverite or sylvanite associated with quartz. 
No fluorite was observed in the ore seen at the time of visit. A specimen of ore 
from the Prince Albert mine was obtained by Penrose in 1894, and the telluride 
within it was examined by Hillebrand and Penfield. It proved to be calaverite.® 
Palache 6 more recently has described a telluride from the Mabel M. mine, and has 
shown it to be sylvanite. The ore, as a rule, is unoxidized, though traces of oxida¬ 
tion can occasionally be detected along some of the more open fissures even in the 
deepest levels. 

PAY SHOOTS AND LODE STRUCTURE. 

With the exception of the main Prince Albert ore body and some small pay 
shoots in phonolite in the Beacon claim, the ore in these mines occurs in narrow 
sheeted zones in granite. The Lindsay lode lies on the east side of a phonolite dike, 
but the ore is all in the granite. There is usually one main fissure, less than an 
inch in width, in which occur quartz and calaverite or sylvanite, the tellurides 
being found in the vugs of the quartz veinlet. This main fissure is often accom¬ 
panied by minor, less persistent fractures, which may also contain quartz and tel¬ 
lurides. The pay shoots are comparatively small, being rarely over 50 feet in 
length and not extending to great depth. The known ore in the Parker & Head 
and Lindsay lodes all occurs at less than 300 feet in depth. In the Mabel M. and 

a Cross, Whitman, and Penrose, R. A. F., jr., Geology and mining industries of the Cripple Creek district, Colorado: Six¬ 
teenth Ann. Rept. U. S. Geol. Survey, pt. 2, 1895, pp. 133-136. 

b Notes on tellurides from Colorado: Am. Jour. Sei., 4th ser., vol. 10, 1900, pp. 419^122. 




MINES OF BEACON HILL. 


361 


Gold Dollar lodes the ore goes deeper, but even in these lodes little ore has been 
found below 350 feet in depth. The pay shoots occur irregularly in the lodes and 
are not, so far as observed, related to cross fissures or intersections. 

The main ore body of the Prince Albert occurs at the intersection of the Prince 
Albert lode with an intrusive sheet of phonolite. This sheet is about 8 feet thick 
and dips north-northeast at an angle of 30°. It is clearly an offshoot from the 
main phonolite mass of Beacon Hill. The ore body, most of which has been stoped 
out, was about 200 feet long and had a maximum width of 40 feet. The general 
relation of the ore to the Prince Albert fissure zone and to the phonolite sill is shown 
in fig. 15 (p. 208). It extended from the surface southwest of the Prince Albert shaft 
down to level 1 of the Gold Dollar mine and is said to have produced over 10,000 
tons of good ore. This ore occurred entirely in the granite, the fissures being prac¬ 
tically barren within the phonolite. A little low-grade ore only has been found in 
the granite on the under side of the phonolite sheet. From a maximum width of 
40 feet, where it rested upon the phonolite, the ore seems to have contracted rather 
abruptly 20 or 25 feet above the phonolite to the narrow width of the Prince Albert 
lode proper, which carried ore up to the surface. 

In the Beacon claim a little ore has been obtained from fissures in the main 
phonolite intrusion. This however, is exceptional, the bulk of the Beacon Hill ore 
occurring in the granite. 

UNDERGROUND WATER. 

These mines were formerly much hampered by water, even at a depth of 200 
feet. The levels were drained by the Standard tunnel and now by the El Paso tun¬ 
nel, though at the time of visit there was stagnant water in the sump of the Mabel 
M. shaft. 


CHAPTER V—MINES OF BULL HILL. 


GENERAL INTRODUCTION. 

Bull Hill occupies a central position in the complex of volcanic hills and many 
important mines are located on its .southern slope. An isolated area of brecciated 
granite occupies its western slope, while over the eastern and southern parts breccia 
prevails. Several bodies of latite-phonolite appear in the breccia. As shown by 
mining developments, these masses as a rule form flat intrusive sheets. In the 
southern area especially the various shafts sunk in it have everywhere shown that 
breccia appears below latite-phonolite at a depth of 300 or 400 feet. Several basic 
dikes with a northwest or northeast trend cut across the southern shoulder of Bull 
Hill, and at least one phonolite dike with northwest trend is prominent in the Logan 
and Dante mines. 

The Wild Horse lode outcrops near the summit and follows approximately the 
contact between granite and breccia, though in lower levels it is entirely in granite 
or granite breccia. On the south or southwest slope a general shattering has 
occurred, as shown by the complicated veins of the Dante, Gold Sovereign, War 
Eagle, and other smaller mines. The strongest fissures appear on the prominent 
south or southeast shoulder of the hill in the northerly trending Blue Bird, Orpha 
May, and Mineral Rock lodes. The Orpha May lode is traceable as a closely linked 
and very productive system for three-fourths of a mile from the Modoc mine, 
by the Last Dollar, Rubie, and Orpha May veins. A basic dike with a north- 
northwest trend cuts across the Orpha May and has in places proved very pro¬ 
ductive. The nortneast slope of Bull Hill contains few lodes of importance. 

WAR EAGLE AND RAMONA MINE. 

The recently opened War Eagle and Ramona property is situated on the south¬ 
western slope of Bull Hill, about 250 feet below the summit. It is worked by 
lessees, who in 1903 extracted a considerable amount of ore from a'surface pit and 
in 1904 opened a vein system found below this surface ore. The production from 
April, 1903, to April, 1904, is stated to be about $45,000. The developments 
consist of the War Eagle shaft, 58 feet deep and connecting on that level with 
the 150-foot Ramona shaft, situated 300 feet to the northeast. The elevation 
of the collar of the War Eagle shaft is about 10,528 feet. The workings are chiefly 
contained in the somewhat shattered granite of Bull Hill, but also reach, near 
W ar Eagle shaft, the breccia contact, which here is sharply defined. A drift has 
been run on this contact for about 100 feet northwest of the shaft. All of the 
rocks are very much oxidized. 


362 


U. S. GEOLOGICAL SURVEY 


PROFESSIONAL PAPER NO. 54 PL. XXV 



A. SOUTH SLOPE OF BULL HILL, FROM SQUAW MOUNTAIN. 
Pikes Peak in distance. 



B. BULL CLIFF AND TOWN OF INDEPENDENCE. 
Vindicator mine to right. 




















MINES OF BULL HILL. 


363 


The veins so far as developed are the War Eagle, striking northeast and dipping 
steeply northwest; the Ramona, striking north-northwest and dipping steeply 
east-northeast; together with several flat seams or small veins. The War Eagle 
vein would seem to be the extreme southern continuation of the Wild Horse vein 
described below, or is at least closely parallel to it. At an elevation of 10,100 feet 
the Xew York tunnel should have intersected the vein, but if it did so the vein 
has not proved profitable. The veins appear as clay seams, the vein matter con¬ 
sisting of soft brown gritty clay with small masses of pure white kaolin. Along 
the flat veins crusts of smoky comb quartz are not uncommon. 

The occurrence of the ore presents several interesting features. A large mass 
was found on the surface somewhat below the vein and almost on top of the granite- 
breccia contact. This, body of thoroughly oxidized ore, which contained values 
of about 825 per ton, had horizontal dimensions of 30 by 40 feet and was not more 
than 25 feet deep. A small bunch of ore yielding 200 tons occurred on level 1, 
on the granite-breccia contact. 

The War Eagle vein has been drifted on for a distance of 400 feet, chiefly north¬ 
east of the shaft, but does not itself contain any ore. The ore occurs for a horizontal 
distance of 200 feet along the intersection with a flat clay vein dipping about 20° 
XW. The shoot followed the intersection closely, the gold occurring chiefly in 
the flat -vein, which at most was 8 feet wide, but not extending far from the War 
Eagle vein. The flat vein, which at first was 10 feet above the level, finally dipped 
under foot. At the Ramona shaft, on the War Eagle vein, another flat vein comes 
in, also dipping 20° XW. and carrying good values at the intersection. The gold 
in the flat veins is comparatively coarse. The central clay seam may assay 8300, 
while the adjacent rock for a foot or two in width contains about 818 to the ton. 

The Ramona vein, which is 2 to 4 feet wide and very clayey, contains a pay 
shoot with very fine gold which begins 8 feet east of the intersection with the War 
Eagle vein and continues for 123 feet west-northwest, being suddenly cut off by a 
partlv open watercourse which cuts across the vein. Diminished values continued 
for a few feet beyond it, but the ore soon became unprofitable. It is believed that 
a fairlv large amount of oxidized ore containing about 86 per ton is available along 
these veins. 

RAMONA NO. 2 MINE. 

This mine is situated on the southeastern part of the Ramona claim, just east 
of the War Eagle mine. Its workings consist of an incline shaft about 200 feet 
deep and three levels, making a total development of about 800 feet. The pro¬ 
duction of the mine could not be ascertained, but it is not large. 

The workings have been driven on a basalt dike which strikes a few degrees 
west of north and has an average dip of 80°. It varies considerably in course, dip, 
and thickness, and here and there pinches out entirely. A short distance north 
of the shaft the dike crosses the breccia-granite contact, the latter lying to the 
north. The change of rock has little apparent effect on the dike. The breccia 
contains much granite and is thoroughly oxidized; the granite is shattered and 
altered, so that the contact between the two rocks can not be exactly located. 
It appears, however, to dip steeply to the north, or in other words the granite 
seems to overhang the breccia. 


364 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

On the third or bottom level the dike is followed northwest from the shaft for 
about 100 feet, becoming here much pinched and shattered. Just north of this 
point the drift crosses a well-defined zone, 3 to 4 feet wide, approximately vertical, 
and striking northeasterly, which contains fragments of granite and plionolite. 
It may be a brecciated-phonolite dike, but the presence of basaltic fragments in 
the zone 50 to 60 feet northeast of the point where the basalt dike was last recog¬ 
nized indicates that this may be a plane of faulting. 

All the ore has been extracted from the basalt dike or the accompanying fissure. 
A little ore was taken from the dike at the surface. On level 1 the granite-breccia 
contact is approximately 20 feet north of the shaft. A little stoping has been 
done above and below the level north and south of the shaft. The vein on this 
level is simply a shattered oxidized zone, holding kaolin, and the basalt is not 
recognized. On level 2 the basalt becomes distinct. The contact is in about 
the same relative position as on the level above. Here also a little stoping 
has been done just south of the shaft, above and below the level. Along and to 
the south of the contact on level 3 a fair-sized stope of ore has been mined along 
the dike, the values being mainly along the sides of the dike. The ore was oxidized 
and of good grade. 

The position, size, and value of the ore shoot seems to be independent of the 
granite-breccia contact, though occurring near and roughly parallel to it. No 
cross seams were observed. 

SHERIFF MINE. 

The Sheriff mine, the property of the Sheriff Gold Mining Company, is located 
on the Sheriff claim, on the saddle between Bull and Raven hills. There are several 
shafts from 100 to 200 feet deep on the property. The principal shaft and the 
only one that was being worked in the spring of 1904 is 300 feet deep and connects 
with about 600 feet of drifting and crosscutting. The production of the mine 
is not very large. 

The shaft is sunk in breccia just outside the Bull Hill granite area. In general 
the rock is fine grained and dense, and appears to be largely phonolitic. A basaltic 
dike is encountered about 30 feet southeast of the shaft, on the 45-foot level. It 
is 18 inches wide, strikes N. 38° W., and dips about 80° SW. On the 165-foot 
level the dike is seen 100 feet southeast of the shaft with the same dip and 
strike, but with a width of 4 feet. Ten feet away and parallel to it is a brecciated 
and oxidized zone containing many fragments of basalt. One hundred feet north¬ 
west of the shaft a 4-foot basalt dike strikes N. 15° W. and dips about 75° E.; it is 
probably a branch from the first-mentioned dike. 

Well-defined continuous veins are not shown by the workings, though several 
narrow seams partly filled with quartz are found in the upper levels. 

The values occur principally in minute seams and veinlets in the dense, unoxi¬ 
dized breccia. These seams are filled with carbonates and carry tellurides. The 
average value of what has been mined is probably $40. 

A small ore shoot descends approximately vertically from the surface. The 
shaft was sunk on it and for a depth of 25 feet extracted practically all the ore 
of the shoot. To the south of the shaft the body expanded and a chamber 20 feet 


MINES OF BULL HILL. 


365 


high, 20 feet east and west, and about 30 feet north and south was stoped out, 
furnishing about $6,000 of $30 to $40 ore without sorting. One of the flat quartz 
seams was reached at the bottom of this chamber, and the values extended only 
a few inches below it. In the shaft, however, the quartz seam was not recognized, 
probably having pinched out, and there the shoot continued down as above. About 
60 feet from the surface it widened out toward the west. At 70 feet the second 
flat quartz seam was reached and the values went only a foot or two below it. 
Ore was stoped out 20 feet above the quartz seam for a width of 20 feet. About 
25 feet west of the shaft a vertical quartz seam was encountered. This seam 
formed the western limit of the ore, but at the junction of the flat and vertical 
veins a small pocket of rich ore was opened toward the south. All the ore from 
this intersection gave returns of $500 per ton and a small shipment assayed 500 
ounces. This intersection was stoped for 20 feet, and the vertical vein carried 
values for 14 feet below the flat vein; then pay ore gave out. 

The central part of this ore body averaged $30 per ton as broken, and the coarser 
wall rock, running $12 to $15, was also mined and shipped. 

A little ore was taken from the 300-foot level, but this was inaccessible at the 
time of visit, and the mode of occurrence was not ascertained. 

BOGART MINE. 

Adjoining the Sheriff mine on the northwest is the Bogart mine of the Mountain 
Boy Gold Mining Company. It has not been worked for some time and was not 
examined. The shaft is 260 feet deep and the workings expose the basalt dike 
which enters the Sheriff ground. Ore is said to have been found where this dike 
splits, and $13,000 was taken from two pockets, the ore averaging $30 to $40 
per ton. 

HAPPY YEAR MINE. 

The Happy Year mine is a short distance north of the Bogart, and contains 
what is without doubt the same basaltic dike. The shaft, which is said to be about 
500 feet deep, is in granite, but most of the workings were inaccessible. A tunnel 
farther down the hill follows the basalt dike and cuts the shaft at about 200 feet. 
The dike is much decomposed, varies from 6 to 30 inches in width, and is about 
vertical. Just north of the shaft a second basalt dike is seen a few feet west of 
the first and nearly parallel with it. The two dikes are said to come together 
above and at the junction to have made a considerable body of ore of rather low 
grade. About 100 feet southeast of the shaft the approximate contact of granite 
with breccia is seen. Both rocks are much altered and the contact is not at all 
sharp. The first-mentioned basalt dike is drifted on perhaps 300 feet south- 
southeast from the shaft. The production of the mine was not ascertained. 

NEW YORK TUNNEL. 

The portal of the New York tunnel, which penetrates Bull Hill, is situated 
at an elevation of about 10,100 feet, close to the eastern branch of Squaw Gulch, 
about 1,800 feet southwest of Midway. The tunnel is 1,500 feet long, with a direction 
of S. 65° E. The rock is granite, but is much shattered and in places holds fragments 
of volcanic material. Several kaolin-filled fissures and seams have been encountered 
and some of them have been drifted on, but, it is stated, without success. 


13001 — No. 54—06 - 25 


366 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


ALBANY TUNNEL. 

The Albany tunnel, on the northwestern slope of Bull Hill, starts about 1,200 
feet southwest of Midway station and is at an elevation of about 10,170 feet. Its 
course is S. 68° E. and it runs for about 1,400 feet in brecciated and oxidized granite. 
Shattered zones carrying kaolin and manganese are frequently seen, running in 
various directions. About 700 feet from the portal an 18-inch basalt dike strikes 
N. 40° W. and dips about 80° SW. The dike is much broken up, and the rock 
decomposed as usual. No ore has been found in the tunnel. 

The Happy Year tunnel was described under the Happy Year mine. 

WILD HORSE MINE. 

The Wild Horse mine, which is controlled by the Woods Investment Company, 
is situated on the northern side of Bull Hill. Ore was discovered in it in 1897, 
and it was actively worked until 1903, when development in depth ceased. At the 
present time the upper levels are leased and low-grade ore for direct cyaniding is 
extracted. It is stated that the production has somewhat exceeded $1,000,000, 
and that about one-fourth of this amount has been disbursed in dividends. 

The developments are very extensive; the vein has been followed for a distance 
of 2,400 feet on various levels. The mine is opened by the Wild Horse shaft, the 
elevation of the collar being 10,653 feet. The lower levels are principally opened 
from the Gleason shaft, which has the same elevation of collar and which is 1,250 
feet deep, level 10 being turned at that depth. Drifts and crosscuts will aggregate 
between 2 and 3 miles in length. The mine never had any water, general drainage 
having preceded exploitation. 

The Wild Horse vein outcrops near the eastern contact of the isolated area 
of more or less shattered granite which occupies the western part of Bull Hill and 
the southern part of Ironclad Hill. Fragments of plionolite are sometimes found 
in this granite and may be due to dikes wholty crushed by secondary movements. 
The rock is oxidized to a depth of 1,150 feet below the surface. As shown in 
the crosscut on level 10, the fresh rock is a loosely cemented breccia, the fragments 
being usually a few inches in diameter and containing plentiful disseminated 
crystals of pyrite. In places a little fluorite may be noted. The contact between 
granitic and volcanic breccia is more or less indistinct on the surface and is not 
exposed in the mine; however, the volcanic breccia usually contains a large amount 
of granitic detritus. Schist begins to appear in the hanging wall of the vein on 
level 4, underneath the Midway station, according to Messrs. Finch and Purington, 
and there are also one or two dikes of plionolite in the older rocks. 

The Wild Horse vein is remarkable in several respects. It is curved, striking 
north-northwest in its northern portion, between Midway and the Wild Horse 
shaft. South of that point it assumes a north-northeast course, and has been 
traced for 1,000 feet to a point not far from the Ramona shaft. Near the Wild 
Horse shaft the apex of the vein lies practically on the contact between granitic 
and volcanic breccia, though it does not follow this contact in depth, but north 
of this point it enters the granitic area. The vein has been traced to a point under¬ 
neath the gap at Midway. The dip is generally steep toward the west. South of 


MINES OF BULL HILL. 


367 


the shafts it is 60° or 70°, but the vein straightens northward to an almost vertical 
position. A small portion of level 2 is said to be driven in volcanic breccia, while 
the workings generally are contained in more or less oxidized granite. 

The vein is ordinarily well defined, with two or more fairly regular walls, which, 
however, are apt to bulge out into swells at places where the ore body is wide. 
Some of the stopes are 25 feet wide. The ore consists of a thoroughly oxidized 
clayey mass, with some pure-white kaolin and a moderate amount of limonite, 
apparently not much more than in the surrounding granite breccia. There is very 
little quartz and the ore can be followed only by assays. The best pay is contained 
in the kaolin seams, some of which run up to $300 per ton, while the hard bowlders 
contain little of value. 

The ore shoot which came to the surface a little south of the Wild Horse shaft 
was very well defined and pitched about 45° N. on the plane of the vein. Near 
the surface the ore w^as low grade and much of this material, suitable for direct 
cyanidation, remains in the upper levels. The length of the shoot along its pitch 
was 1,200 feet, while the horizontal dimension along the levels varied from 200 
to GOO feet; the greatest length being attained on level 5. Good and poor parts 
w r ere irregularly distributed; the richest stope, yielding $200,000, was near the 
bottom, above level 9, 970 feet below 7 the collar; this v r as 40 feet long and 27 feet 
v T ide. Between levels 8 and 9 the ore became stringy and thin. 

Level 10, turned 1,250 feet below 7 the collar, showed the rock unoxidized; 
the crosscutting to the vein w 7 as greatly interfered with on account of gas, wdiich 
sometimes filled the w r hole mine for days. At the end of the crosscut the vein 
w'as found, it is stated, but consisted chiefly of a loose mass of iron pyrites of little 
value. It was not, how-ever, extensively explored. The pyritic granite breccia 
in the crosscut contained values up to $4 per ton. The lower levels have remained 
closed since 1903. 

LONDONDERRY MINE. 

The Londonderry mine is located on Ironclad Hill close to Mkhvay. It has 
not been w 7 orked for many years, and very little ore has been extracted from it. 
The shaft is 300 feet deep, and its collar has an elevation of 10,550 feet. It is sunk 
in granite and schist and some drifts run on a vein presumably parallel to and 
west of the Wild Horse. The workings also extend a few 7 hundred feet east to 
the Wild Horse vein. 

GOLD SOVEREIGN MINE. 

The Gold Sovereign Mining and Tunnel Company owrns several fractional 
claims on the southwestern side of Bull Hill. The company has produced ore from 
tw r o localities, viz, the Lovett vein and the Whisper block. The latter occurrence 
will be described in connection with the Dante mine, as the two properties here 
exploit the same set of veins. The total production to 1904 w 7 as $300,000, of which 
$100,000 w 7 as contributed by the Whisper part of the property. A new and verj^ 
rich shoot w 7 as exploited in 1904 near the Lovett vein. 

The developments consist of the Gold Sovereign tunnel, driven for 640 feet in 
a northeasterly direction, the elevation of the portal being about 10,001 feet, and 
the Jackson shaft, which opens the Lovett vein and is at present leased to the 


3'68 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

Cripple Creek and Gold Temple Company. The elevation of the collar of this 
shaft is about 10,150 feet and the depth 645 feet. Seven levels have been turned, 
the seventh and deepest being 550 feet below the collar. The total extent of drifts 
and crosscuts is over 2,000 feet. 

The country rock along the Lovett vein is latite-phonolite. Breccia occurs only 
on the southwest side of the vein, in the stope north of the shaft on the third level. 
A basic dike with a north-northwest strike follows the trend of the vein for the entire 
distance developed—about 600 feet; it also appears to the north in the Maggie pros¬ 
pect and to the south in the Trilby mine. It is not well shown on the surface. The 
width is rarely over 4 feet. In places it splits into two parallel dikes. While 
ordinarily much decomposed, fresh rock is obtainable in places. The dark, fine¬ 
grained rock contains large foils of biotite and the microscope shows it to be a mon- 
chiquite. A narrow phonolite dike also follows the trend of the vein and lies 
generally on the east side of the basic dikes. 

The so-called Lovett vein is rather an ill-defined, almost vertical zone of fracture 
up to 50 feet wide than a single clear-cut vein. The trend is N. 40° W. It is crossed 
by the Fox vein, trending N. 60° E. and dipping steeply to the southeast! The Fox 
vein first appears 300 feet west of the Lovett, where it is exposed by a short tunnel, and 
is next cut by several drifts from the Jackson shaft, but has not been found on the 
lowest or seventh level. It continues for several hundred feet toward the northeast 
and is also exposed in the Whisper block. In character it is a narrow sheeted zone, 
1 or 2 feet wide, carrying fluorite and quartz along its central fissure. Besides these 
two principal veins there are a number of flat seams, generally dipping southwest and 
exercising a decided influence on the ore bodies. 

The ore occurs chiefly where flat seams intersect the Lovett vein or near the 
intersection of the Lovett and the Fox veins. It does not occur in the basic dike nor 
in the phonolite dike, but may be found on either side of them. Most of it is entirely 
oxidized, but on the lowest level calaverite is contained in the narrow seams. 

Ore was found along the apex of the Lovett vein from the croppings of the Fox 
vein southward to the Lovett shaft, a distance of 200 feet. On the third or 250-foot 
level, 100 feet northwest of the shaft, there was a large ore body having dimensions of 
100 by 100 by 20 feet. The stope was opened on a flat vein at the intersection with 
the Lovett vein, chiefly on the northeast side of the latter. There are two basalt 
dikes here 10 feet apart, but no ore occurs in them. Little else of value is found on 
this level. On level 4, 300 feet below the collar, the drift follows the basic dike south 
to the Fox vein, which seems to be locally interrupted by the dike; there is no proof, 
however, that the dike is really later than the vein. A good shoot 20 feet long has 
been stoped on the Fox vein up to the surface; it lies between the basic dike and the 
parallel phonolite dike. Two hundred feet south of the Jackson shaft the basalt dike 
crosses over to the west side of the Lovett vein. At this place is a stope in latite- 
phonolite about 35 feet long on the level and 2b feet wide with particularly rich 
streaks, changing in position from one wall to another. This stope extends nearly 
to the surface. 

The continuation of the same stope has been opened from level 7, 550 feet below 
the surface. Here the phonolite dike, 12 feet wide, lies on the east side of the basic 
dike. Very rich ore was found in 1904 in latite-phonolite between these dikes; the ore 


¥ 


l \ 


MINES OF BULL HILL. 


309 


body is at least 8 feet wide and contains calaverite in little fissures and spaces of 
dissolution. In the center of this ore body appears a flat fluorite seam, 6 inches 
wide, with a central veinlet of quartz. A few feet west of this point, near the basic 
dike, wholly oxidized ore has been stoped 100 feet high. Several hundred carloads 
were taken from this part of the shoot. Many small flat seams of great richness 
occurred in this stope, all dipping northwest. 

TRILBY MINE. 

The Trilby mine is situated on the western slope of Bull Hill, just south of the 
Gold Sovereign. It is owned by the Moose Gold Mining Company and is located on 
the Trilby fraction, which contains only four-tenths of an acre. The shaft is 585 
feet deep, with 500 feet of drifts and crosscuts. Development work is in progress. 
The production is estimated at about $30,000. The mine is now being operated 
under lease by the Bayard Mining and Leasing Company. 

Weathered latite-phonolite with its characteristic pitted appearance is disclosed 
in surface workings. The short upper levels of the mine were not visited. The 
country rock of the 400-foot level and below is breccia, in general only slightly or not 
at all oxidized. A basalt dike which shows no well-defined outcrops at the surface, 
but is exposed in the Trail workings on the south and the Gold Sovereign on the north 
crosses the property near the shaft. It appears to be irregular, and while only one 
dike is seen on the 400-foot level, there are three with corresponding position, 
direction, and dip on the 480-foot level. 

Between the eastern and middle basalt dikes on the 480-foot level is a shattered 
mass of phonolite fully 15 feet wide. It contains a few fragments of breccia, but 
probably represents the phonolite dike which parallels the basalt in the Gold Sov¬ 
ereign workings. This phonolite was not observed on the 400-foot level. 

On the upper levels some ore was stoped from pockets in the basalt dike. Thirty 
feet west of the shaft, on the 400-foot level, the narrow basalt dike appears striking 
N. 15° W. and dipping 85° W. It is drifted on to the north* for 20 feet to the Gold 
Sovereign line, where the dike has widened to 6 feet. Near the line a stope has been 
made 6 to 12 feet wide and 20 feet high, at which height the values gave out. A 
15-foot winze 15 feet from the line is in good ore. 

Between the 400-foot and 480-foot levels the shaft cut a narrow oxidized seam 
which is vertical and strikes a little east of north. Just above the 480-foot level its 
dip changes to about 75°. Just south of the shaft on this level the vein widens and 1 foot 
of basalt comes in. The dike is said to be good ore at this point. Another basalt 
dike, 15 or 20 feet west of the shaft, has a steep dip to the west and strikes N. 15° W., 
corresponding in direction with the dike on the level above. It is being stoped to the. 
south and gives $30 to $60 ore. When visited the stope was 20 feet high and 30 feet 
long. Toward the south the basalt narrowed and at last pinched out completely, and 
in the breast a 3 to 4 inch quartz vein, characterized by druses and vugs and carry¬ 
ing values of $300 to the ton in tellurides and free gold, had taken the place of the 
basalt. This quartz seam may be the same as that noticed on the level above. 

Between this dike and that at the shaft is a dike-like zone of shattered phonolite. 
In the numerous minute seains tellurides occur, with occasionally free gold also, 
making this an ore body worth $20 to $50 per ton. 


370 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


Thirty feet west of the shaft is a 1-foot basalt dike parallel to the second one; 
it is not drifted on as yet, but is said to constitute ore. No developments had been 
made on the 580-foot level. 

The values seem to be intimately associated with the dikes, but no other condi¬ 
tions, such as cross veins or junctions, seem to influence the distribution of the 
pockets and pay shoots in these dikes. 

TRAIL MINE. 

The Trail mine is situated on the southwestern slope of Bull Hill, just south of 
the Trilby. It is at present controlled by the Woods Investment Company. The 
mine has not been regularly worked for some time, but formerly received considerable 
exploitation, though the production has not been great. The workings consist of a 
vertical shaft about 500 feet deep and several levels, of which only the two tunnel 
levels are accessible. 

Both breccia and latite-phonolite occur in this mine. As in the Blue Bird, Gold 
Sovereign, and Trilby, the latite-phonolite appears to flatly overlie the breccia. The 
contact between the two is usually indistinct through brecciation of the latite- 
phonolite, but in the lower Trail tunnel the contact is sharply defined and dips flatly 
southwest. Numerous phonolite dikes, economically unimportant, are encountered 
in the various workings. Their direction is variable, but usually is between north 
and west. Three basalt dikes of a general northerly course are cut in the lower 
tunnel. One of them corresponds in position, strike, dip, and width to the basalt 
dike which passes through the Trilby and Gold Sovereign mines. 

Each tunnel follows a nearly north-south vein which dips steeply to the west. 
It is said and seems probable that they are on the same vein, though the vein in the 
lower tunnel has a 4- to 10-inch streak of dense fluorite, while that above appears as 
only a narrow crack in oxidized rock. There are short stopes, timbered so that their 
height can not be ascertained, in several places along each tunnel. Eighty feet south 
of the shaft, on the upper tunnel level, a “mud vein” dipping steeply west and strik¬ 
ing a little east of north crosses the main vein and is said to have made the best ore in 
the mine. The stope is not large. A stope 50 feet long, 25 feet deep, and 20 feet 
high has been opened just north of the shaft on the main vein. The ore was of 
medium grade. 

DANTE MINE. 

The Dante mine, together with the Whisper block of the Gold Sovereign mine, is 
situated near the High Line track on the southwestern slope of Bull Hill, at an eleva¬ 
tion of about 10,350 feet. The Jackson shaft of the Gold Sovereign mine is located 
about 700 feet southwest of the Dante shaft. The Dante Gold Mining Company, 
owning the Dante claim, is controlled by the Reed Investment Company, of Colorado 
Springs, but the property is worked by a number of lessees; sometimes as many as 
eight sets are at work. The production is considerably over $100,000, and a similar 
amount has been produced by the adjacent Whisper block. 

The developments consist of the Dante shaft, 450 feet deep, from which six 
levels are turned. The various veins are opened by a complicated network of 
drifts and crosscuts, probably aggregating 4,000 feet on both properties, but not 
extending beyond a circle with a diameter of 400 feet. The Whisper block of the 


MINES OF BULL HILL. 


371 


Gold Sovereign is developed by the Whisper shaft, 475 feet deep, and now being 
deepened further. It is 175 feet north-northwest of the Dante shaft. There are 
seven levels, the lowest 390.feet below the collar. The elevation of the lowest 
level is thus only 9,960 feet, while the Jackson shaft is down to an elevation of 
9,505 feet. 

On the surface latite-phonolite prevails, much of it in the form of loose slide 
rock, at least for 70 feet below the ground. The lower levels are generally in breccia, 
but this contains much latite-phonolite, and the line between the two formations 
is not distinct. A phonolite dike 25 feet wide and striking a few degrees west of 
north traverses the property between the two shafts and is exposed on several levels. 
This dike continues on the north into Logan ground. On the second level of the 
Whisper an equally wide dike of a peculiar latite-phonolite adjoins the phonolite 
on the east. 

The veins as a rule are narrow, consisting of a central seam with quartz, cala- 
verite, and a little fluorite; on both sides of this seam there are usually a few less 
distinct parallel cracks. The north¬ 
easterly trending Fox vein contains 
more fluorite than the others. The 
ore is mainly oxidized, but calaver- 
ite begins to appear in the lower 
levels. At least nine veins have 
been found on the property. Their 
relative positions are illustrated in 
fig. 42. Trending north or north- 
northwest are the Parallel, Whisper, 
and Blue Bird veins. The Parallel 
strikes north-south and stands 
nearly vertical. The Whisper strikes 
N. 30° W. and dips 60° SSW. The 
so-called Blue Bird has the same 
strike, but dips 70° NNE. Among 
the northeasterly trending veins the 
Fox strikes N. 60° E. and dips steeply 

south-southeast. The Moffat and Fig ' 42 ~ Vein systems in Whisper and Dante mines, chiefly on 
, _ . . . . i-i level 4,240 feet below the surface. 

the East veins, neither ot which 

carry much ore, strike N. 40° E. and stand about vertical. The Fox, Whisper, 
and Parallel are the principal productive veins known from all levels. 

The occurrence of the ore is strikingly dependent upon vein intersections. 
One of the principal shoots occurs along the intersection of the Parallel and Whisper 
veins, a line descending at a moderate angle toward the south and crossing the 
Whisper shaft at about level 4. Most of the ore was found on the Parallel vein. 
On level 7 the intersection is found 140 feet south of the Whisper shaft on the line 
separating that property from the Dante mine. Smaller stopes have also been 
opened on the Whisper vein at some distance from the line of intersection. Another 
ore shoot lies along the line of intersection of the Fox and Whisper veins, which 
dips southwest. At the intersection of the Fox and an unnamed vein parallel 










372 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


to the Whisper ore occurred between levels 6 and 7. Some ore occurs in the dike 
of latite-phonolite on level 2 of the Whisper shaft. Along the west side of the 
phonolite dike on level 6 of the Dante lies another vein which has produced a little 
ore. Ore has also been extracted from the Blue Bird vein on levels 4 and 5. In 
its prolongation this vein would enter the Blue Bird claim a short distance south¬ 
east, but it is not on§ of the main Blue Bird veins. 

BLUE BIRD MINE. 

The Blue Bird Gold Mining and Milling Company owns the Blue Bird claim, 
on the southern slope of Bull Hill. The developments consist of one main vertical 
shaft 1,350 feet deep, with the elevation of collar 10,397 feet, several smaller shafts, 
and about 8,000 feet of drifts and crosscuts. Fifteen levels are turned, the lowest or 
level 151 having an elevation of 9,048 feet. The production is stated to be $300,000. 
The mine was located and worked at an early date. When Penrose visited it in 
1894, it had already attained a depth of 300 feet. 

The country rock on the surface and down to level 4 is latite-phonolite, but at 
about that depth it is replaced by breccia, so that the massive rock seems to form 
a horizontal sheet above the breccia. A phonolite dike about 20 feet wide, with 
the usual platy parting, cuts across the southern part of the claim. Its trend is 
north-nortliwest, and it is probably the same dike which has been noted from the 
Dante and Logan mines. A small northwesterly trending basic dike was observed 
near the southern face of level 4 and not far south of the phonolite dike. Active 
oxidation has penetrated along the veins down to level 4. On the ninth and lower 
levels there is not much oxidation. 

The main vein strikes about N. 5° E. and dips 60° to 90° E. in the upper levels. 
Below level 9 the dip changes to westerly, soon, however, resuming its easterly 
inclination. Locally the vein changes abruptly in strike and dip and is associated 
with much irregular fracturing, dominantly north-south, but of various dips. Some 
east-west fissures occur which do not fault the vein and which carry no one. Two 
shorter, almost vertical veins parallel to the main Blue Bird vein have been devel¬ 
oped in the northern and southern parts of the claim; each is 100 feet distant from 
the main vein, the one to the east, the other to the west. They have been opened 
only to level 4. 

The ores of the Blue Bird have always contained much silver; in places assays 
will give several hundred ounces to the ton. Copper carbonates were found on the 
upper levels. The first appearance of tetrahedrite, which is the principal argentif¬ 
erous mineral, was on level 10. Below the oxidized zone the gold appears in cala- 
verite or sylvanite, which occur chiefly in cracks in the massive fluorite of the vein, 
or in vugs in the same material. Tetrahedrite occurs massive with fluorite or in 
quartz, sometimes intergrown with missive tellurides; it is also found in medial 
vugs in spar veinlets in the deeper levels. It carries both gold and silver and is 
locally accompanied by a little pyrite. Stibnite is mentioned by Penrose from the 
upper levels. Nests of white kaolin,- while common in the upper levels, are not 
known below level 5. The vein material in the main fissure is a compact, fine¬ 
grained mixture of purple fluorite and quartz, which no doubt is formed by the 
filling of open cavities; it contains sharply angular inclusions of little-altered coun- 


MINES OF BULL HILL. 


373 


try rock. This material is sometimes 3 feet in width. Secondary fracturing with 
opal and drusy quartz is often noted, and the ore seems to be associated with these 
disturbances. In places, such as in level 10, the vein appears as a sheeted zone 6 
feet wide, divided in slabs about a foot thick. On level 4 the fissures pass through 
the phonolite dike, but no values are contained in the dike. On the twelfth and 
lower levels the vein shows fine parallel sheeting, with a great number of veinlets of 
dolomite which carry fluorite and tetrahedrite. The slight developments on level 
15 show again the large fluorite vein with sharply defined inclusions of breccia. It 
is seen here that the spar veinlets are younger than the compact fluorite. 

The main vein is opened for 900 feet horizontally, but the deep developments 
are confined to the vicinity of the shaft and a few hundred feet south of it. The 
surface shoots on the main vein extended down to level 6, 400 feet deep. One part 
seems to dip about 45° N.; the maximum length along the levels was 400 or 500 feet. 

A smaller, northerly shoot almost connecting with this seems to dip southward, 
but extended only to level 3. From level 11 down to the bottom ore is stated to 
occur again. Some very fine specimens of tellurides and tetrahedrite have been 
found in this part of the mine. 

DEXTER MINE. 

The Dexter mine, situated on the Dexter claim, lies to the south of the Blue 
Bird, on the southwestern slope of Bull Hill. It is owned by the Dexter Gold Mining 
Company and is being worked under lease. Sinking was in progress at the time 
the mine was visited, the shaft being then 560 feet deep. Four levels have already 
been turned and a station cut for the fifth. The elevation of the collar is about 
10,300 feet. Three other shafts on the property, now abandoned, increase the total 
developments to about 3,000 feet. The production of the mine has not been very 
large. 

The shaft starts in the pitted, oxidized latite-phonolite which is characteristic 
of this slope of Bull Hill. As in the near-by mines, this rock is found to overlie brec¬ 
cia as a flat sheet. Level 1 is closed. Level 2, 200 feet below the surface, is in 
breccia, but the top of a 40-foot stope above this level shows the approximate con¬ 
tact of the two rocks. Three hundred feet S. 15° W. of the shaft on level 2 the con¬ 
tact is again seen, breccia to the east and latite-phonolite to the west. The contact 
is by no means sharp and its dip and strike could not be determined. A dike of 
latite-phonolite 20 feet wide crosses the level about 145 feet south of the shaft. The 
remaining workings of the mine are in breccia. 

The veins of this mine belong to one very well-defined system, apparently 
corresponding to the westernmost of the three Blue Bird veins, a short distance to 
the north. They trend slightly east of north and dip very steeply to the west. 
One of these veins just west of the shaft, called the Fluorite vein, is a sheeted, 
partially oxidized zone in breccia, with kaolin and a brownish-black manganese 
oxide in the seams and a 2- to 8-inch seam of dark-purple fluorite sometimes carrying 
quartz. Fifteen feet farther west is a nearly parallel vein carrying more manganese 
and no fluorite, but otherwise similar. This is known as the Manganese vein. 
About 100 feet south of the shaft, on the 280-foot level, these two veins come 
together and continue for 50 to 60 feet, when they finally cross and resume their 
former courses. A 50-foot crosscut, east from the shaft on the same level, reaches 


374 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


another vein of this system. It is similar in character to the others and holds 
kaolin, manganese, and soft, muddy fluorite in the seams. A fourth parallel vein, 
with manganese and much kaolin in the seams, occurs 120 feet west of the shaft, 
on the third or 320-foot level. 

North of the shaft, on level 2, the Fluorite vein carried ore, the values occurring 
principally in the seams as rusty gold. The vein is stoped at this place 3 to 4 feet 
feet wide, 40 feet long, and 40 feet high. 

A small amount of ore was taken from the Manganese vein directly west of 
the shaft, on level 2. On level 3 this vein is good ore, but has not yet been much 
developed. 

Where the Fluorite and Manganese veins unite on level 2 a good body of ore 
has been formed. The rock is oxidized and considerably shattered and the values 
occur in the seams. The rock is reported to average $14 as mined, and the screen¬ 
ings are of better grade. A stope 60 feet long and averaging 10 feet wide had been 
carried up 40 to 50 feet at the time of visit. The ore is said to continue to the 
surface. This is the main ore body of the mine, and it is the intention of the leasing 
company to erect a cyanide mill to treat it. The breast of the drift on the Fluorite 
vein on level 3 was about 130 feet south of the shaft, and good values were just 
beginning, probably indicating the proximity of the Manganese vein. These two 
veins have been cut on level 4, but have not 3 ^et been developed. 

The vein east of the shaft on level 2 is crossed just north of the crosscut by 
a narrow vertical seam, which is not observed elsewhere. At the intersection a 
couple of carloads of ore were taken out. 

LAST DOLLAR MINE. 

PRODUCTION AND DEVELOPMENT. 

The Last Dollar Gold Mining Company owns the Last Dollar and Combination 
claims, covering an area of IS acres. The mine is working on veins which lie in 
the general southward continuation of the Orpha May and Rubie vein system, and 
which, south of the Last Dollar, appear in the Modoc mine. The total production 
from April, 1896, when the property was acquired by the present company, up to 
March 1 , 1906, is $2,090,396. Early in 1904 the mine was hoisting 100 tons per 
day and shipping 30 tons of ore per day. 

The developments consist of a main vertical shaft 1,268 feet deep (in 1904), 
the elevation of the collar being 10,278 feet. Twelve levels are turned, the lowest 
1,218 feet below the collar. The total length of drifts and crosscuts is probably 
10,000 feet. South of the main shaft are three inclines called A, B, and C. B is 
the deepest, reaching down to level 6. The developments are almost entirely 
confined to the Last Dollar claim. The mine had some water a few years ago, 
but in 1904 the bottom level was dry. 

GEOLOGICAL FEATURES. 

The country rock in which the Last Dollar vein occurs is chiefly a syenite, at 
many points going over into latite-phonolite by gradual transition. Phonolite 
dikes are not uncommon, especially on level 12. Breccia occurs on levels 4 and 5 
on the west side of the Modoc vein. 


MINES OF BELL HILL. 


375 


LODE SYSTEMS. 

The Last Dollar and the Modoc veins form on this claim a practically con¬ 
tinuous system of linked veins, striking N. 10° to 25° W.; they are either vertical 
or dip very steeply westward. A number of short cross veins intersect the Last 
Dollar veins on both sides of the main shaft; their trend is N. 50° to 60° E., and 
their dip very steep, say 75° NW. Actual intersections were not seen, but Mr. 
Charles Walden, the manager, states that the Last Dollar veins cut across the 
sulphide veins, and would thus appear to be the later of the two. 

ORES. 

The principal gangue minerals are a slightly greenish dolomitic mineral, with 
some fluorite and quartz. Above level 8 the ore is entirely oxidized, but below it 
calaverite is probably the most important ore mineral. Tetrahedrite, rich in silver, 
occurs on the Modoc veins and on the short northeast veins crossing the Last 
Dollar veins. Pyrite, zinc blende, and mol} r bdenite, with a little galena, also 
occur on these cross veins, while they are practically absent from the Last Dollar 
veins. 

Some of the stopes are 20 feet wide; a width of 4 or 5 feet is, however, more 
common. The structure of the veins is that of sheeted zones, in which, within a 
space of a few feet, there are up to 20 or more narrow, parallel carbonate and 
fluorite seams on which the calaverite occurs. The ore extracted in the mine is 
screened and washed, the coarse part being rejected as waste, while the screenings 
are of high grade. The cross veins have a similar structure in which a central 
seam, with vugs and pseudomorphic quartz is often prominent. Sometimes the 
central fissure will be filled by fluorite, several inches wide. The Modoc veins 
contain little fluorite. 

PAY SHOOTS. 

* 0 

The most important ore shoot follows the intersection of the cross vein with 
the Last Dollar veins at the shaft, and thus dips 75° N. on the plane of the latter. 
The most productive part thus far exploited occurred in this shoot, between levels 
4 and 8, but the shoot has proved rich as far down as the present developments 
have been carried—that is, to level 12. The greatest horizontal length of this 
shoot is 250 feet. Rich bodies of ore also occurred at the intersection with the 
main vein of several other cross veins located farther south, near shaft C (fig. 43). 
On the cross veins sulphides and tetrahedrite prevail, but it is believed that in these, 
too, the principal value lies in the calaverite. Pay ore extends on these cross veins 
up to a distance of 40 feet from the Last Dollar veins. 

On the Modoc veins a shoot was stoped from the surface down to level 6, and 
recently good ore has been found on the same vein system on level 10. Explora¬ 
tions in the northern part of the claim have discovered some bunchy ore, but no 
regular shoots. 

DETAILS OF THE LAST DOLLAR VEIN SYSTEM. 

The Last Dollar vein really consists of three branches, which appear to unite 
300 feet north of the shaft. There are practically no developments north of the 
shaft above level 4. The easterly branch, 75 feet east of the shaft, stands practically 


376 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


vertical, and is opened for 250 feet north and south of the shaft, between levels 
4 and 8. A westerly branch, not known on the upper levels, then appears; it passes 

a few feet west of the shaft, and has been 
developed on levels 9, 10, 11, and 12. 
Between the two lies a shorter branch, 
chiefly known from levels 8 and 9. The 
two main branches seem to split about 250 
feet south of the shaft. Beyond the junc¬ 
tion, 300 feet north of the shaft, the Last 
Dollar vein has been developed only on 
levels 5 and 11. It is poorly defined, some¬ 
times showing only as a number of tight 
slips in the rock, and has a tendency to turn 
off to the west. At a small stope 400 feet 
north of the shaft, on level 5, the vein shows 
as a seam of fluorite 2 to 5 inches thick, with 
several subordinate parallel cracks. On 
level 11, 550 feet north of the shaft, a frac¬ 
tured zone, which probably corresponds to 
the main vein, contains fluorite and dolomite 
carbonates with scattered values. One hun¬ 
dred and fifty feet east of this point the 
extreme workings on this level have opened 
a narrow seam, rich in spots, with fluorite 
and tetrahedrite. 

On the Last Dollar veins the ore consists 
chiefly of tellurides, with dolomite gangue, 
also some fluorite and quartz, the whole 
forming a sheeted zone 3 or 4 feet wide. 
Open spaces are not common. Tetrahe¬ 
drite is reported from a winze on level 12, 
on the main vein, but elsewhere seems 
largely confined to cross veins. 

The cross veins are at least four in num¬ 
ber. The first and most important crosses 
the shaft at about level 6 and is traceable 
from the surface down to the bottom level. 
It contains much fluorite in places, as well 
as vug holes along a central seam. On level 
12 the second or south cross vein contains 
open spaces as much as 2 feet wide and 12 
feet long. Secondary action by silica solu- 
Fig. 43.—Vein system of Last Dollar mine, on levels 5, tions, resulting ill pseudomorpllS of quartz 

after dolomite and celestite, is common. 
Massive pyrite, with zinc blende, tetrahedrite, and molybdenite, commonly occurs on 
the cross veins, but the values do not extend more than 40 feet from the main vein. 











MINES OF BULL HILL. 


377 


On level 12 a strong cross vein is cut 125 feet south of the shaft, being probably 
the same that appears on levels 5 and 6. Just west of the main vein this intersects 
a number of short veins trending a little more northwesterly than the main vein. 
This southerly cross vein has been followed out to the side line of the claim, but 
the values soon decrease, though pyrite and zinc blende still occur in its seams. On 
some of the levels the cross veins south of the shaft are not well developed. 

Aside from some small ore bodies on levels 5 and 11, north of the shaft, the 
principal pay shoots occur at the intersections of the main vein with the first and 
second cross veins. The shoot at the main shaft has been followed 1,200 feet 
down; on the various levels it is up to 250 feet long along the main vein, and pay 
extends out on the cross veins for a distance of 40 feet at most on both sides. 
On the bottom level ore is said to extend for 180 feet north and 240 feet south of 
the shaft, establishing in fact a connection between the shoots on the north and 
south cross veins. Ore has been found also on various upper levels at the inter¬ 
section of the cross veins south of the shaft, but it does not form as well defined a 
shoot as that near the main shaft. 

In the upper three levels, now inaccessible, the main shoot lies just south of 
the shaft and at the intersection of the cross vein with a vein of the Modoc system, 
between the two branches of the Last Dollar vein. From levels 4 to 8 it jumped 
across to the intersection with the easterly of the Last Dollar veins, while from 
levels 8 to 12 it was transferred to the intersection with the westerly branch of 
that vein system. 

DETAILS OF THE MODOC SYSTEM. 

The Modoc veins are at least three in number and lie in the general continua¬ 
tion of the Last Dollar veins, but have a more decided westerly dip of 75°. The 
easternmost is opened on level 5 at the south end line of the claim, but is here , 
unprofitable. It is the same as No. 2 vein in the Modoc mine, on which pay ore 
occurs. A central vein, the same as No. 1 or the principal vein in the Modoc mine, 
cropped on the surface for 400 feet and is opened by the three incline shafts A, B, 
and 0, the second being the deepest and extending to level 6. This vein contained, 
between the surface and level 3, an ore shoot of fair proportions, which below level 
3 becomes smaller and shows a tendency to pitch south. Between levels 5 and 6 
the ore contained much copper and silver, indicating a partly oxidized tetrahedrite. 
The vein shows large vugs in a central seam, filled with loose material and coated 
with quartz and dolomite. Alunite, a secondary mineral, fills the medial seam in 
places. 

The developments on level 10, the next one below level 6 in this part of the 
mine and the deepest at present, have shown the existence of rich ore with some 
tetrahedrite on this narrow vein. A third of the Modoc vein system has been 
opened in the extreme southwest corner of the claim. 


378 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


MODOC MINE. 

PRODUCTION AND DEVELOPMENT. 

• 

The Modoc mine, on the Ocean View claim, is owned by the Modoc Mining 
and Milling Company, and is situated a few hundred feet south of the Last Dollar, 
on the eastern slope of the broad gap separating Bull Hill from Battle Mountain. 
The property has been worked constantly since 1897 and has been a steady pro¬ 
ducer and dividend payer. Efforts to ascertain the total production have failed, 
but the mine has probably yielded approximately half a million dollars. 

The shaft, which is situated near the north end of the claim, is vertical for the 
first 110 feet and then changes to a steep incline down to level 11, a total vertical 
depth of 675 feet. From level 11a winze 400 feet deep extends down to level 15, 
which at present is the deepest. The elevation of the collar is about 10,150 feet, 
and the total depth 1,075 feet. Developments aggregate about 6,000 feet. Levels 
7 and 9 extend practically through the entire claim, while those above and below 
are confined to the north end, except level 15, which is 800 feet long. At present 
(1904) work was carried on only from level 9. The mine has no water in the bottom, 
but gas fills the winze 200 feet and sometimes 400 feet deep. 

GEOLOGICAL FEATURES. 

- The syenite area of the Last Dollar mine changes to breccia near the north 
end line of the Modoc property, and breccia continues as the principal country 
rock until the southern part of the claim is reached. The rock is of normal appear¬ 
ance and often contains much phonolite, but on the bottom level it is said to be 
loose and sandy, with open caves in places. A phonolite dike not more than 20 
feet thick has been followed for 300 feet on level 9, 600 feet south of the shaft. A 
large and irregular mass of the same rock appears on the same level 200 feet farther 
south; it seems to be about 100 feet wide and extends at least 148 feet below level 
9; possibly it is connected with the first-mentioned dike. The southern face of 
level 9 is in breccia. 

VEIN SYSTEM. 

The Modoc vein Xo. 1 is followed underground for 1,300 feet, almost from one 
end of the claim to the other. It is a narrow sheeted zone about 4 feet wide; the 
foot-wall seam is usually well defined, as is sometimes also a hanging-wall seam. 
Where the vein traverses phonolite, it seems less sharply defined, but the ore widens 
considerablv. The vein curves slightlv eastward, so that while at the north end 
the strike is X. 20° W. it has changed to X. 10° E. in the southern part of the prop¬ 
erty. The dip is constantly 75° to 80° W. A shorter and parallel vein called Xo. 
2 is opened on the east side near the shaft on level 9 and on several of the upper 
levels. Many short seams cross the main vein, trending northeasterly near the 
shaft and southeasterly in the southern part of the claim. Xo faulting was observed 
at the intersections. A distinct but barren vein follows the first phonolite dike, 
600 feet south of the shaft; its strike is northwest, its dip 70° XE. 


MINES OF BULL HILL. 


379 


ORE. 

The general character of the Modoc ore is like that from the main vein of the 
Last Dollar. The narrow seams in the vein contain quartz, with a little dolomite, 
and are coated by tellurides. There is very little fluorite. The oxidation extends 
in places down to the bottom level, while some fresh tellurides were found as far 
up as level 2. In many places the veins contain a contact seam filled with a hard 
white substance which proves to be impure alunite, a potassium-aluminum sulphate, 
probably formed by oxidizing influences. There is little silver on the upper levels, 
but more on the lower; some tetrahedrite was found on level 15. In the southern 
shoot the ore contains as much as 28 ounces of silver per ton. A little zinc blende 
occurred on one cross vein, but the strong development of sulphides on these veins, 
so prominent in the Last Dollar, seems absent here. More pyrite occurred in the 
lower levels, but was here, too, associated with calaverite. The ore is of the usual 
high grade. At present a wide body of ore is mined at the south end of the claim, 
being taken out 18 feet wide in places. The screenings only are kept, but these run 
upward of 4 and as high as 8 ounces per ton. The ore in the phonolite is as good 
as that in the breccia. 

ORE SHOOTS. 

The ore in the Modoc vein, as in the Last Dollar, seems to depend on its inter¬ 
section with cross veins or with joint systems having a northeast or southeast 
strike. The ore extends only a few feet on these from the main vein. Some ore 
has been mined from vein No. 2, but the most important part of the production has 
been derived from the main vein near the shaft. The stopes on the main vein 
extend to within 100 feet of the surface and to all of the lower levels except 14 
and 15. On level 9 they are 150 feet long. A parallel shoot lies on the No. 2 vein, 
a short distance east of the main vein. To the south, on level 9 there are three 
smaller shoots, all occurring at intersections with cross joints; one is now being 
mined in phonolite from a winze 150 feet below level 9 and 850 feet south of the 
main shaft. 

RUBIE MINE. 

The Rubie property, adjoining the Last Dollar on the north, has been exploited 
under lease by the Princess Alice Gold Mining Company. Work was discontinued 
a few years ago. 

The Rubie shaft is located 1,450 feet north-northwest of the Last Dollar shaft. 
It is about 800 feet deep, with drifts extending 300 feet north and 500 feet south. 
Three hundred and fifty feet to the south a winze has been sunk to an approximate 
depth of 400 feet. The main drifts follow a vein with occasional bunches of ore 
which lie in the direct northward continuation of the Last Dollar vein. The vein 
is vertical or dips very steeply to the east. At the winze mentioned a northeasterly 
trending cross vein intersects the main vein, and here a narrow pipe or chimney of 
good telluride ore was found, averaging in value about 860 per ton. This narrow 
shoot extended through a vertical distance of 400 feet. It had a rounded cross 
section, with a diameter of from 7 to 30 feet, was contained in breccia, and seemed 
to represent an old water channel. The gangue consisted of quartz, chalcedony, 
and fluorite. 


380 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


STRATTON PROPERTIES ON BULL HILL. 


SITUATION AND DEVELOPMENT. 


The holdings on Bull Hill of the Stratton Cripple Creek Mining and Develop¬ 
ment Company, or of Stratton’s estate, as it is commonly designated, form an 
irregular .area reaching practically to the summit and covering parts of the southern 
and eastern slopes of that prominent point; irregular projecting points include the 
Longfellow claims on the southeast and the Los Angeles mine on the south. On the 
northeastern side the property includes the Zenobia mine, which adjoins the Phar¬ 
macist. The total area is approximately 200 acres. 

The production was derived chiefly from the Orpha May, Mineral Rock, and 
Shurtloff No. 1 veins; accurate figures have not been obtained, but the total amount 
is considerable. From Hills’s Manual the following data are obtainable; they extend 
only to January 1, 1900, but very little ore has been mined on the properties in 
question since that date. 

V . 

Approximate production of certain claims of Stratton mines. 


Los Angeles 
Lucky Guss 
Sacramento 
Specimen .. 


$100,000 
327, 000 
10,000 
125,000 


Zenobia. $141, 000 

Orpha May and Pikes Peak (Union Gold 

Mining Company). 1, 000, 000 

Favorite. 75.000 


The production of Shurtloff No. 1, Logan, and Mineral Rock mines has not been 
ascertained. 

During the first part of 1903 the Shurtloff No. 1 was worked to some extent 
through the American Eagle shaft, but in the early part of 1904 the entire system 
was idle. Work on the Shurtloff is reported to have been resumed in the latter part 
of 1904. Most of the following notes, except those on the Zenobia, are from reports 
of men formerly connected with the various mines, from a study of the surface, and 
from data obtained from the underground maps. 

The developments are very extensive and comprise a total length of drifts, 
crosscuts, and shafts of at least 60.000 feet. Aside from a great number of smaller 
shafts there are three deep ones—(1) the John A. Logan, 1,400 feet deep, elevation 
of collar 10,472 feet, of sump 9,097 feet; (2) 950 feet east by south of this is the 
Orpha May, 1,264 feet deep, elevation of collar 10,538 feet, of sump 9 274 feet; (3) 
1,200 feet north by west of this is the American Eagle, 1,500 feet deep, elevation of 
collar 10,750 feet, of sump 9,249 feet. All of these are connected by a remarkable 
system of crosscuts and drifts, developed according to the far-reaching plans of 
W. S. Stratton. Level 15, the deepest in the American Eagle, corresponds to level 
12 of the Logan and level 17 of the Orpha May. 


WATER AND GAS. 

The bottom levels of the mines are dry. Gas has proved very troublesome in 
the Logan mine, especially in a crosscut on level 12, 500 feet northwest of the shaft, 
where it issues in large volumes. It is also said to be bad in the long east crosscut on 
level 13 in the Orpha May mine. 










MINES OF BULL HILL. 


381 


GEOLOGICAL FEATURES. 

Volcanic breccia in places containing much latite-phonolite occupies the largest 
part of the area; but, as may be seen from the map, the area of massive latite-phono¬ 
lite which covers the surface at the Gold Sovereign, Blue Bird, and Dexter mines 
throws out a wide branch northward on the west side of Bidl Hill, almost reaching its 
summit at the Zenobia mine. This body of intrusive rock rests like a thick sheet on 
breccia, in which are most of the underground workings. A short distance east of 
this latite-phonolite, which may be called the Blue Bird area, appears another which 
is designated as the Altman area. This seems to reach down as far as the under¬ 
ground workings in the Findley mine have penetrated—1,500 feet. Whether the 
Shurtloff No. 1 vein is in breccia or latite-phonolite on level 15 of American Eagle 
has not been ascertained. At any rate, latite-phonolite must begin a short distance 
east of it. 

A very prominent phonolite dike about 25 feet wide traverses the Logan work¬ 
ings with a north-northwest trend; it lies 200 feet west of the shaft and is cut by 
levels 3, 5, 10, and 12. A parallel dike is stated to lie 50 feet west of the shaft. The 
main dike continues through the Dante workings and is probably continued through 
the Blue Bird and possibly into the Colorado City mine. It forms part of the great 
phonolite-dike system of the Portland mine and may be identical with the Rigi dike 
crossing the southern part of the Modoc mine. In the Logan it is not reported 
to carry values. 

Two persistent basic dikes cut through the central part of the properties in the 
Orpha May mine, and one of them at least is traceable on the surface for 2,000 feet. 
The western dike is exposed in the Favorite workings, where it dips steeply east- 
northeast; then in various crosscuts between the Eagle and Logan shafts, and finally 
in the Orpha May workings, where it is very productive and is intersected at an 
acute angle by the Orpha May vein. The other dike lies 200 to 300 feet farther 
northeast and is exposed by long drifts on Orpha May level 13 and Logan level 5. 
This does not seem to carry much ore. 

The Isabella dike of dark trachydolerite is said to be intersected by the Ameri¬ 
can Eagle shaft between levels 2 and 3. 

VEIN SYSTEMS. 

Several important vein systems traverse the property and at least three of them 
appear to converge toward a point from 500 to 800 feet north of the American Eagle 
shaft. Nearly all the veins trend north-northwest to north and stand vertical or 
dip a few degrees to the west. The Zenobia is the only one 6f importance which 
strikes northeast. 

Beginning from the west the productive veins are as follows: 

LOGAN VEIN. 

The Logan vein is exposed on various levels near the shaft and trends north- 
northwest. It is said to have carried ore for 200 feet below the surface. The lower 
workings disclosed many veins in various directions like those of the Dante, but no 
ore shoots of importance are recorded. 

13001—No. 54—06-26 



382 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


The “Basalt” vein following the Orpha May dike trends about N. 32° W., but 
with considerable local deviations. The dip is nearly vertical or, in the Favorite 
mine, 75° E. In the latter ground it proved productive at least down to level 5. 
A nonproductive interval follows, and then, just northwest of the intersection with 
the Orpha May, good ore again occurred on it. Much ore was stoped from levels 9, 
10, and 11, probably also on higher levels, but from 11 to 17 little ore is reported 
from this vein. 

ORPHA MAY VEIN. 

The Orpha May vein for 800 feet south of the American Eagle shaft trends due 
north; it then turns to N. 15° W. and continues with this strike through the Orpha 
May workings to the Lucky Guss and thence down through the Rubie to the Last 
Dollar and Modoc, a total distance of a little less than 1 mile. The vein is not 
continuous throughout, but is replaced at intervals by closely contiguous fissures. 
The dip is vertical or very steeply westward, as shown in the Porcupine shaft. The 
lode has been opened on several levels from the American Eagle shaft but is appar¬ 
ently not traceable far north of it; in this ground it is said to be nonproductive. It 
is next shown in the shallow Grouse shaft and 600 feet south of the American Eagle 
shaft, in the Porcupine incline, where it has been explored to level 6 and appar¬ 
ently produced ore. For 1,000 feet south of this point it has been developed by the 
Orpha May workings to a depth of 1,260 feet. Penrose describes the Orpha May 
vein as a fissured zone in massive volcanic rock, and shows four well-defined but 
short shoots on it down to the 97-foot level. The shoots are said to be more likely 
to occur where cross fissures intersect the main vein, which is interesting in 
view of the fact that the same holds true for the whole southern course of the lode 
through the Last Dollar and Modoc. The vein appears to have continued down to 
the bottom level, but little ore is reported on it below the upper levels. 

MINERAL ROCK VEIN. 

The Mineral Rock vein lies, with slightly divergent strike, a few hundred feet east 
of the Orpha Maj^. It begins 550 feet north-northwest of the American Eagle shaft, 
where it strikes nearly north-south, as shown on level 5 of this shaft. From a point 
300 feet north-northwest of the American Eagle shaft its course is very straight at 
N. 22° W. to the south end. It is opened by the following inclines, each about 500 
feet deep, indicating an extremely steep westerly dip: Mineral Rock, Garfield, Pikes 
Peak, Orpha May No. 2, and Lucky Guss No. 2. Its northern part is also crosscut 
by levels 5 and 8 of the American Eagle shaft. It is opened by drifts on level 5 to 
a point 400 feet south of the Mineral Rock incline, and on levels 5 and 8 to a point 
700 feet north of it. Levels 11 and 15 of the American Eagle crosscut it, but no 
drifts have been run. About 300 feet south of Lucky Guss No. 2 its continuation 
has been crosscut bj^ level 11 of Findley shaft, but whether the same vein actually 
exists here is doubtful. 

Penrose describes the Pikes Peak or Mineral Rock lode on page 196 of his report, 
saying that it consists of a zone of Assuring 3 to 4 feet wide; the vein itself is from 1 
inch to 1 foot wide, wholly oxidized to the depth then attained—197 feet. The 
sheeted zone in places follows a phonolite dike from 1 inch to 18 inches thick. Near 
the surface it splits into three distinct veins. 


MINES OF BULL HILL. 


383 


There were several ore shoots along this vein, and some of them have been sloped 
to a depth of 500 to 600 feet. It is stated that little of value has yet been found 
below this depth. The best ore was obtained from Lucky Guss No. 2, which was 
opened to level 7 and was crosscut in two places by level 13, Orplia May shaft. The 
ore is stated to have continued down to level 6. 

SHURTLOFF VEIN. 

Shurtloff No. 1, a nearly vertical vein trending N. 36° W., has been opened for 
800 feet by crosscuts from the American Eagle shaft on levels 5, 8, 11, and 15. Rich 
ore has been found on the latter three levels 900 feet east by south of the shaft. 
Tetrahedrite is reported to occur on the lowest level, which is 1,300 feet below the 
place where the vein should outcrop. The Findley veins lie a short distance to the 
east and have proved productive to at least 100 feet below level 15 of the American 
Eagle shaft. 

Two veins which evidently lie in the same general zone as the Shurtloff vein 
have been intersected in the long Orpha May crosscut on level 13, 1,100 and 1,200 
feet east of the shaft. 

The Zenobia vein is described in connection with the Pharmacist and Burns 
mines (p. 401). 

LOS ANGELES VEIN. 

% 

The old Los Angeles mine is situated between the Blue Bird and the Last 
Dollar; the Portland holdings adjoin it on the south. It has been idle for many 
years, "but in 1905 several thousand tons of low-grade oxidized ore was extracted 
and treated by direct cyanide process. 

MINES NEAR CAMERON. 

The lower northern slopes of Bull Hill and Bull Cliff near Grassy Creek and the 
little town of Cameron are characterized b} T the prevalence of much comparatively 
fresh breccia of reddish-brown color and well-preserved fragments. The Isabella 
dike of trachydolerite extends down to Grassy Creek and has here been proved some¬ 
what productive, though elsewhere it is entirely barren. 

No great mines are situated in this vicinity, but the Pinnacle has a very credit¬ 
able production, and blocks 8 and 10 have likewise proved profitable. The Morn¬ 
ing Star, which is situated somewhat higher up on the slope, nearer to the Isabella, 
was worked in 1903 on a small scale by lessees, but closed later on. On the north 
side of Grassy Creek in this vicinity there are no developments of importance. 

PINNACLE MINE. 

The Pinnacle mine is situated on the northern slope of Bull Hill, above Cameron, 
at an elevation of 10,250 feet. Between 1897 and 1900 it produced about $250,000. 
The mine is developed by an incline shaft 100 feet deep, a vertical shaft 500 feet 
deep, and about 1,800 feet of drifts and crosscuts. It was closed in 1904. 

The principal workings occur in breccia, but the contact with the latite-phonolite 
is reached in several places. The main vein of the mine is a sheeted fissure in 
breccia, striking northeast and dipping northwest. Another vein said to carry 


384 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


quartz occurs to the southwest of this vein, with about parallel strike. A cross vein 
carrying fluorite intersects the main vein about 300 feet north of the vertical shaft. 

The principal ore shoot began at the mouth of the incline shaft and extended 
southwesterly for 180 feet. It pitched to the southwest on the plane of the vein 
and crossed the vertical shaft at about the 06-foot level. At 140 feet the size and 
value of the ore body was very much diminished, but some work continued below 
that point. No ore was found below the 250-foot level. The richest part of the 
shoot occurred 125 feet below the surface, where the ore body was 25 feet wide and 
about 120 feet long. In most places the ore is about 4 feet thick. A small body 
of ore was taken out at the intersection of the main vein and the fluorite vein above 
the 173-foot level. 

The ore was oxidized in all places except a small core where the ore body had 
its greatest width and where calaverite appeared. The value of the ore was high, 
running up to 76 ounces per ton. A 300-ton lot of 10-ounce ore was shipped at one 
time. 

BLOCK 8, SCHOOL SECTION 16. 

The tract of State land known as block 8, school section 16, is situated on the 
lower slope of Bull Cliff, near Grassy Creek, and east of Cameron. A lease on the 
property is being worked by La Montaigne Brothers, who in two and a half years 
have taken out about $85,000, which represents the total production of the mine. 

A shaft 550 feet deep has levels turned from the 250, 350, and 550 foot points, 
the total development amounting to nearly 3,000 feet. < 

The principal rock of the mine is characteristic breccia, frequently pinkish or 
reddish, with remarkably little pyritization and alteration. In places, however, it 
is gray and more compact and can not always be easily distinguished from massive 
rock. Two basaltic dikes are exposed on the surface and appear in the underground 
workings. One of them, with a northeast strike, and dipping steeply northwest, 
passes about 150 feet east of the shaft. It can be traced down the hill to the creek 
and up the hill to the Isabella mine and corresponds in appearance to the dike seen 
there, being fresh and black, with noticeable phenocrysts of pyroxene. It is a 
trachydolerite and is 8 to 15 feet wide. The workings underground show that the 
course of the dike is not constant. It appears to veer more to an east-west course 
with increasing depth. 

The other dike, which is seen about 75 feet north of the shaft, has an east- 
northeast course and a dip which is on the whole about 85° S., though it is slightly 
inclined here in one direction, there in the other direction, from the vertical. This 
rock is more decomposed, but where fresh is a dense black aphanitic rock, which the 
microscope shows to be probably in the class of monchiquites. 

The crossing of these two dikes is not seen on the surface, but as they dip together 
the intersection is exposed on the 250-foot and again on the 450-foot level, and in 
both places the east side of the smaller dike is faulted about 10 feet to the north by 
the larger. This narrow basalt dike seems to have been intruded along a fissure 
earlier filled by a latite-phonolite dike. The width of the latite-phonolite is not 


385 


MINES OF BULL HILL. 

shown, but it is in several places cut and crossed by the basalt. It is seen on all 
levels but the first. 

A second latite-phonolite dike 4 to 5 feet wide and practically parallel with the 
first is seen just south of the shaft on levels 2, 3, and 4. 

Two hundred feet south of the shaft, on the 250-foot level, ore occurs in the 
larger basalt dike and for a foot or two on each side in the country rock. The values 
consisted of tellurides distributed in small seams and fractures. The rock was 
screened and the screenings, which formed a small proportion of the whole, shipped 
at $60 per ton. The stope at this place is 25 feet long, 15 feet wide, and about 45 
feet high. 

On the 350-foot level 150 feet south-southeast of the shaft a small pocket of 
similar ore occurred on the large dike, and a stope was carried 20 feet below the 
level 8 feet wide and 15 feet long. On the 450-foot level stoping above the level 
was in progress at the time of visit. The values here extend for a short distance 
out into the breccia. 

No ore shoot of importance or persistence has been found on this dike. The 
ore occurs in bunches or pockets, at the edges of which the values decrease in all 
directions. No conditions influencing the concentration of gold-bearing minerals 
at these places were observed. 

On the 250-foot level the workings explore the intersection of the two basalt 
dikes and the fault by which the larger one dislocates the smaller. On the west 
side of the fault plane a body of ore occurred along the small dike, which is here 
considerably decomposed. The ore carried both tellurides and free gold derived 
from them by oxidation. Although the sorted ore averaged 4 to 5 ounces, the 
valuable minerals were so disseminated that they could only rarely be seen. The 
stope is 35 feet long, 5 feet wide, and extends 20 feet above and 20 feet below the 
level. It yielded $4,000. 

On level 2 another body of ore was encountered northeast of the main shaft. 
The values, mainly tellurides, occurred in the seams of the “basalt,” and particularly 
near the latite-phonolite dike. The screenings were ore, and averaged about 20 per 
cent of the total rock broken in the stope. Their value was about $60 per ton. 

The stope is 150 feet long, 5 to 6 feet wide, and extends from 40 feet above 
level 2 down to level 3, a total of 150 feet. Below level 3 the grade of ore was 
too low to be profitably mined. 

On the bottom level a 250-foot drift on the small dike under the stope above 
encounters only $10 ore and no stoping has been done. 

The latite-phonolite dike just south of the shaft has been drifted to the south¬ 
west, on level 2, and though some fair assays were obtained, no ore was found. 
On level 3 the dike is not prospected, but on level 4 it contains ore and drifting 
had just commenced at the time the mine was visited. The contact at each side 
is sharp and distinctly marked by a narrow veinlet. Small druses partially filled 
with comb quartz carry tellurides, which also occur in the seams of the dike. The 
surrounding breccia contains finely disseminated pyrite, but, except within an inch 
or two of the dike, does not carry values of importance. 


386 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

C 

BLOCK 10, SCHOOL SECTION 16. 

A lease is being worked on block 10, school section 16, situated near Grassy 
Creek, just north of block 8. The workings consist of a vertical shaft 250 feet 
deep, with one level at the bottom representing 300 to 400 feet of prospecting. 

A crosscut to the southeast reaches, about 50 feet from the shaft, the large 
dike seen in block 8. It is here 8 feet wide and about vertical. Parallel with it 
on the northwest side is a mass of phonolite, probably a shattered phonolite dike. 
Twenty-five feet farther to the southeast is a dike of dense reddish phonolite. 
Beyond it is the smaller dike seen in block 8, and just to the southeast of it is a 
2-foot oxidized vein, with seams and stringers of manganese. Low-grade assays 
have been obtained from this dike. A drift runs southwest for 200 to 300 feet 
along the large basalt dike, and two crosscuts have been run southeast to the smaller 
dike and the vein. No ore has been found. 

The shaft on block 7, which lies between blocks 8 and 10, was closed and not 
-entered. It was worked under lease some time ago by the Woods Investment 
Company. They are said to have taken out 130,000 from a shoot between the two 
basalt dikes, which are here close together. The shoot pitches toward block 10, 
but the values gave out at a depth of 165 feet. 


1 


# 


CHAPTER VI— MINES BETWEEN ALTMAN AND GOLDFIELD. 

ISABELLA EODE SYSTEM. 

The first important lode system encountered when the Altman-Goldfield dis¬ 
trict is approached from the northeast is situated on the slope of Bull Cliff. The 
prevailing country rock is the usual fine-grained pyritic breccia, which, however, 
farther down on the north slope shows only a very slight degree of alteration. An 
intrusive area of latite-phonolite surrounds the veins in part. From the sections 
and descriptions given below its dike-like form, spreading near the surface to wider 
proportions, is clearly apparent. A very persistent dike of trachjnlolerite cuts across 
the lode system with a northeast strike (fig. 44). 

The two mines described below, the Isabella and the Victor, were among the 
large earlier producers, and still continue to show a small output. Their north¬ 
westerly trending system of lodes is shown on fig. 44 and, like so many others, is 
characterized by a slightly divergent direction of individual veins. A depth of 
1,200 feet has been attained in the Isabella and somewhat less in the Victor. The 
Buena Vista vein of the Isabella mine is especially persistent. 

VICTOR MINE. 

PRODUCTION AND DEVELOPMENT. 

The Victor Gold Mining Company owns the Victor and Little Joe claims, on 
the northeastern slope of Bull Cliff. The total production is given as $2,216,671 
to January 1, 1900, and the dividends paid to the same date $1,155,000. The last 
dividend was paid in December, 1898, and during the last few years the mine has 
been idle, except for a little leasing work in the upper levels. Shipping was resumed 
in July, 1904, and ore is reported to have been found on levels 5, 6, 8, 9, and 10. 

The developments comprise the Victor vertical shaft, 1,800 feet southeast of 
the Lee shaft of the Isabella. The elevation of the collar is 10,547 feet, and the 
total length of drifts, shafts, and crosscuts between 2 and 3 miles. Fourteen levels 
are turned. Level 8 is only 429 feet below the collar. The lowest level is said to 
be about 1,000 feet below the collar. 

GEOLOGICAL FEATURES. 

The prevailing country rock on the surface and in the workings is a normal 
volcanic breccia, usually of fine grain. The trachydolerite which covers Bull Cliff 
does not appear in the workings. It is reported that a flat mass of phonolite was 
encountered on the lower levels. 

VEIN SYSTEM. 

The Victor veins trend northwest and show a tendency to diverge northward. 
The dip is 70° or steeper southwest. On level 5 the main vein is traced 550 feet 

387 


388 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE (’REEK DISTRICT. 


southeast of the shaft. Two hundred feet 



northwest of the shaft the vein branches. 
The East Victor vein continues, with 
a strike of N. 52° W. and dip of 68° 
SW., for 400 feet to the end of the 
claim, and then on level 3 for at 
least 400 feet farther into Isabella 
ground. The West vein is of less 
importance. Close to the Victor 
shaft is another junction from which 
diverges a connecting vein between 
the Victor and the Cheyenne system, 
at first with a strike of N. 80° W., 
but farther on in Isabella ground 
swinging about to a more north¬ 
westerly strike. The dip is steep to 
the southwest. It is developed on 
Victor levels 7, 8, 9, and 10. 


s 

a j 

CO 

CO 

s 

> 

tii 

*3 

& 

w 

H 

T5 

G 

c3 

t-4 

o 

+■> 

o 

> 

© 

& 


C 

Pu 

s 


2 


tioned. Crosscuts 120 feet below level 


OCCURRENCE OF THE ORE. 

The ore is said to have been oxi¬ 
dized throughout in the Victor work¬ 
ings, with the normal gangue of 
quartz, fluorite, limonite, kaolin, 
and manganese oxides. Little is 
known of the distribution of the 
ore. The most important shoot 
seems to have occurred within 400 
feet on both sides of the shaft, near 
the point where the veins diverge. 
In depth the shoot became impov¬ 
erished; it is stated that, like the 
Cheyenne shoot of the Isabella mine, 
a flat mass of plionolite was encoun¬ 
tered which cut off the ore. At the 
northwest end line where the East 
Victor vein enters Isabella ground a 
very rich shoot occurred, the stopes 
of which were visited. It is in places 
30 feet wide and extended down 40 
feet below level 5, or 280 feet below 
the surface. There exists in the 
breccia at this point a system of 
flat joints which much resemble a 
rude stratification and which cut 
off the shoot at the depth men- 
5 failed to find ore in Isabella ground. 













MINES BETWEEN ALTMAN AND GOLDFIELD. 


389 


ISABELLA MINE. 

PRODUCTION AND DEVELOPMENT. 

This property, owned by the Isabella Mines Company, consists of about sixteen 
claims forming an irregular area of 160 acres on the northern slope between Bull 
Cliff and Bull Hill. It was one of the most, productive mines of the camp from 
1895_to 1900. In 1899 the output reached the maximum, $968,000. The total 
sum is between $3,000,000 and $4,000,000, and dividends have been paid to the 
amount of $675,000. For the last few years the mine has been worked in a small 
way by lessees. 

The mine is opened by the vertical Lee shaft, from which fourteen levels are 
turned. The elevation of the collar is 10,460 feet, and of the sump 9,332 feet. 
The first eight levels average 70 feet apart, while from 8 to 14 the distance between 
them is 100 feet. Level 3 is 202 feet below the collar; level 7, 438 feet; level 8, 
520 feet; level 10, 720 feet; level 14, 1,120 feet. The Buena Vista incline is sunk 
on the vein 800 feet north-northwest of the Lee shaft, and follows it down to level 7. 
Level 3 corresponds with Victor level 5, and level 11 *with Empire State level 11. 
The workings on the Pharmacist or Maloney and the Empire No. 2 veins are described 
on pages 393 and 395. There are several miles of drifts and crosscuts, chiefly on 
the Buena Vista and Cheyenne veins, which have been opened for a horizontal 
distance of 3,400 feet. 

GEOLOGICAL FEATURES. 

The croppings of the Buena Vista vein are chiefly in breccia, though between 
the Buena Vista and Lee shafts they run close to the contact of a southeastern 
projecting wing of the area of latite-phonolite which may be noted on the map on 
the northern slope of Bull Hill. For a few hundred feet southeast of the Lee shaft 
they cut through this dike-like wedge, and then continue into breccia to the Victor 
mine. 

All the drifts from the Buena Vista incline and the ten upper ones from the 
Lee shaft show latite-phonolite, while breccia prevails on levels 11, 12, 13, and 14. 
These relations are roughly shown in figs. 45 and 46. From the latter it appears 
that the intrusive mass has really the form of a dike, gradually widening toward 
the surface and dipping steeply to the southwest. 

The breccia is generally of normal character, with small but well-defined 
fragments of phonolite and latite-phonolite. It is apt to become harder and less 
pyritic some distance away from the veins, as shown in the long crosscut in the 
hanging and foot walls on levels 7 and 11. In the southeastern part of the mine 
the breccia is light colored, fine grained, and contains flat joints which in places 
clearly follow a rude stratification. The breccia near the phonolite sheet on the 
Cheyenne vein contains many fragments of that rock. Granitic fragments are 
said to be very abundant on level 14 (at present under water), and it was even 
stated that massive granite occurred on that level in the crosscut to the Cheyenne 
vein. 

A thick sheet of phonolite with a flat northwesterly dip is encountered in the 
workings south of the Lee shaft on levels 10, 11, and 12. A smaller sheet, also 


390 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


dipping northwest, is encountered on levels 10 and 11 below the projection of the 
Buena Vista incline. The same intrusive body is probably met in the long crosscut 


FT. ABOVE SEA LEVEL 
10600 


-5 muggier incline 


Buena Vista incline 

I 

Surface 


tee shaft 



0 . 


\ +■ , /■o’*’ v . + + Qj i *C -f- , . 

V Co A' + + ' ~o- : o K ^ ' 

v \ /o ,* + n + 5V/& *+ 4 . + 

'"i/g *' *, * <- * -+■ ' \ + 

. /:£—J-.+ f / -t- * /+ + \ * ^ + 






t- \ -*■ / 




/ -V 


0) 

> 


Leve/ // 


* ♦ -*■ + 


BRECCIA 


Q_ 

E 

(D 

O 


/* ♦ • 

/♦ + 

/«- •* 


"Z eve/ /4 


(under water) 


9200 


Breccia 


►' + n h 
,+\. 


Latite - phonolite 


Phonolite 


10,600 


- <0 


Fig. 45.—Longitudinal projection of the Buena Vista and Cheyenne veins of the Isabella mine. 

in the foot wall on level 10, 250 feet southeast of the collar of the Buena Vista 
incline, at the point where the Isabella basalt dike cuts through it. A third very 

large body of the same rock, with a prob¬ 
able flat southeasterly dip, begins a short 
distance northwest of the Maloney vein 
on level 11, and is also shown on level 
10 north of the crossing of Empire No. 2 
vein, which cuts through it for a long dis¬ 
tance. A very persistent but narrow 
dike of trachydolerite, called the Isa¬ 
bella dike, cuts through the workings 
between the Lee and Buena Vista shafts 
and is especially well exposed on level 
10 in a long crosscut in the foot wall. 

VEINS. 

The principal vein system trends N. 
40° W. and the fissures dip southwest 
at 60° or steeper. This system is crossed 
by several northeasterly trending veins. 
The most important and most continuous 
of the northwesterly trending veins is 
called the Buena Vista; from the upper workings this vein would seem to be con¬ 
tinuous with the East Victor vein, and it has been followed on several levels for 



Fig. 46.—Cross section of the Buena Vista and East veins at 
the Lee shaft, Isabella mine, looking northwest. 


/ 















































































MINES BETWEEN ALTMAN AND GOLDFIELD. 


391 


1,600 feet north and 500 feet south of the Lee shaft. The farthest point to which 
it has been traced is 1,550 feet northwest of the Lee shaft on level 11, but it is not 
known on the surface above this point. There is, however, in this vicinity a small 
vein dipping 30° N. on which the Comet incline, 100 feet long, has been sunk and 
a little ore obtained. The dip, as shown in fig. 46, is fairly regular, averaging 65°. 
Southeast of the Lee shaft, and on the lower levels, the Cheyenne veins join the 
Buena Vista, but farther to the southeast swings away from it, assuming a strike 
of N. 40° W. The Cheyenne is followed on many levels 1,200 to 1,400 feet south¬ 
east of the Lee shaft; in the lower levels it is steep, but flattens out above level 7. 

The three branches of the Victor vein in the southern part of Isabella ground 
strike about N. 60° W. and the westerly branch practically intersects the Cheyenne 
on level 10, but they do not persist farther than a point 600 feet southeast of Lee 
shaft. The East vein lies 100 feet northeast of the Buena Vista and is opened near 
the Lee shaft on levels 9 to 13. A third parallel vein has been cut on levels 13 
and 14, 100 feet nearer the shaft (fig. 46). 

Among the northeasterly trending cross veins the Empire No. 2 intersects the 
Buena Vista on levels 9, 10, and 11 about 500 feet north of Buena Vista incline, 
but has not been followed far on the foot-wall side. The Pharmacist intersects 
on levels 9, 10, and 11, 250 feet north of the projection of the same incline. Its 
apex should cross the Buena Vista near the incline, but is not known here. A 
smaller cross vein was noted at the incline on level 5. The Klondike vein, striking 
N. 10° E. and nearly vertical, is known only on the seven upper levels, 400 feet 
southeast of the Lee shaft. On levels 10, 11, and 12 this is replaced about the 
same distance from the shaft by the vertical Campbell vein, which strikes N. 35° E. 

With one exception no faulting is noted at intersections in the cross veins. At 
the Klondike crossing, however, south of the Lee shaft, the Buena A r ista vein has 
been faulted from 20 to 50 feet, the southeastern part being thrown to the west. 

OXIDATION. 

The original water level was unusually low in the Isabella, 900 feet below the 
collar being the figure given. As a consequence oxidation has followed the veins 
down to the bottom level, 1,100 feet below the collar, though, in the lower levels, 
much calaverite was mined with the free gold. In the massive rock on both sides of 
the Buena Vista incline tellurides were found on level 2, and in places on lower levels 
of that incline the vein is almost free from oxidation. 

ORE AND VEIN STRUCTURE. 

The oxidized ores are of normal character—a soft mixture of ferruginous clay, 
pure kaolin, and quartz, with occasional seams of manganese, all carrying rusty gold. 
Fluorite is rarely abundant, the calaverite generally being contained in quartz-lined 
seams with occasional vugs. Tetraliedrite occurred in most of the levels of the 
incline from 2 down. It has also been found on the same Buena Vista vein at the 
junction with the Cheyenne on level 11, a short distance north of the crosscut from 
the Lee shaft. 


392 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


All the veins show the usual type of narrow, sheeted zones, sometimes with only 
one prominent central seam. The Cheyenne on level 3 shows as a single seam of 
entirely oxidized ore. On level 7 the Cheyenne and West Victor veins lie closely 
together and two systems of seams appear, one dipping 70° SW., corresponding to 
the latter, and the other very steep, corresponding to the former. On level 10, where 
the Cheyenne vein was very rich, it appeared as a streak of brown mud 3 to 4 feet 
thick, composed of crushed quartz and limonite. On level 11 the well-defined vein 
with seams of fluorite dipping 60° SW. is a barren brecciated zone 2 to 4 feet wide. 
On the t.wo lowest levels the oxidized vein remains well defined by several strong 
seams, but the mineralization seems less prominent than on the upper levels. 

The Buena Vista vein on the various levels of the incline is a sinuous and narrow 
sheeted zone, at most 6 feet wide, and in many places very seamy and brecciated. 
Fluorite is present locally as a central veinlet, up to 6 inches wide. The seams are 
generally coated by quartz and more or less open. On the lowest levels this vein 
continues through breccia and phonolite as a system of narrow seams from 2 to 3 
feet wide, but becomes less distinct toward the north. At the crossing with the 
Empire State No. 2 the Buena Vista vein is not well defined. There is a slight 
alteration of the country rock in the sheeted zones by the introduction of pyrite and 
dolomite, but it rarely masks the character of the rock. The East vein is similar 
to the Buena Vista. The Klondike and Campbell cross veins, about 400 feet south¬ 
east of the Lee shaft, are vertical sheeted zones with little evidence of mineralization. 
On level 12 the latter is very wide and carries values of low grade. 

ORE SHOOTS. 

On the Victor vein system, in Isabella ground, there are at least six well-defined 
shoots. The southernmost, the West Victor, carries a small ore body reaching to 
250 feet below the surface and dipping 45° NW. On the East Victor vein in the 
same vicinity a rich shoot extended into the Isabella from Victor ground, also 
pitching northwest and attaining a width of 30 feet. It gave out 350 feet below the 
surface and is said to have stopped at flat seams in the breccia, some of which 
carried ore themselves. 

Next follows the big Cheyenne shoot, on the vein of the same name. It begins 
on level 3, 1,200 feet southeast of the Lee shaft, and continues, pitching 45° NW., to 
a line 25 feet below level 10, where it encountered a large body of dense phonolite in 
which it rapidly impoverished. The richest ore was found at this point, and 
furnished a carload of 27£ tons which is reported to have yielded $219,000. 

The Klondike and Campbell cross veins have yielded no shoots of importance, 
though small bunches of ore may occur on them close to the Buena Vista Vein. 

The shoots on the latter number three. The first is a narrow vertical chimney 
beginning on level 11, 400 feet south of the Lee shaft, and continuing to the surface, 
widening out here considerably and practically connecting northward on level 3 with 
the next shoot just north of the shaft. The second is also a vertical chimney at most 
100 feet in length, the width of ore on all of the shoots averaging 3 feet. It begins 
on level 12 and, like the first, widens on level 3, connecting with the Incline shoot so 
that near the surface there is an almost continuous ore body 1,600 feet long. The 
Incline shoot also begins on level 11 and is stoped continuously with greatly 


\ 


MINES BETWEEN ALTMAN AND GOLDFIELD. 


393 


varying width to the surface. Near the surafce the stopes are very extensive, reach¬ 
ing 10 feet in width. On level 12 small spots showing values are encountered below 
the principal shoots. The East vein contains a few small stopes; one was seen on 
level 14, 500 feet south of the shaft. 

Summing up, we have, then, on the Victor system in Isabella ground, three 
shoots dipping at 45° NW. and three others about 90°, on the plane of the vein. No 
definite laws governing their occurrence could be found. It is true that one of the 
vertical shoots nearly coincides with the crossing of the Campbell and jClondike 
veins, but no similar causation can be adduced for the remaining two. The ore 
almost invariably pinches when dense, normal phonolite is met. 


MIXES BETWEEN TIIK 


VICTOR AND YINDICAT()It VEIN SYSTEMS. 


GENERAL RELATIONS. 

The two great systems of linked veins named respectively the Victor and the 
Vindicator both trend northwesterly and are separated by a space 1,500 feet in 
width. This space within a distance of 3,000 feet contains a number of smaller 
mines, most of which are working on veins with a northeasterly strike. Some of these 
veins continue up to the Isabella veins of the Victor system, but they are not as a 
rule productive on the northeast side of that system. The following mines, named 
from north to south, are described: Empire State, Pinto, Burns, Wrockloff, Pharma¬ 
cist, Zenobia, Mercer, Murphy, Puehlo, Wacu Weta, Deadwood, Trachyte, Pearl, 
Deadwood No. 2, and Delmonico. 

Two basic dikes, classified as vogesite, cross the Empire No. 2 and Pharmacist 
veins with northwesterly strike; one of them, the Pinto dike, has been productive in 
the Wrockloff mine and at the intersection with the Pharmacist vein. The same 
dike probably'appears in the Deadwood No. 2 mine. The veins do not differ 
markedly from the ordinary type of sheeted zones; they often carry much fluorite. 
The country rock is breccia, with irregular masses of latite-phonolite and smaller 
bodies of phonolite. No marked influence of the inclosing rock is shown in the ore 
shoots, except that the veins often become less productive when entering the dense, 
normal phonolite. The most northerly of these veins is the Empire No. 2 or Emma 
No. 2, which continues with a strike of N. 78° E. and steep northerly dip for 1,200 
feet west of the Buena Vista vein in the Victor system. The second is the Phar¬ 
macist vein, extending, with a strike of N. 50° E. and dip of 60° NW., from the 
Zenobia to the Isabella vein, a total distance of 1,600 feet. It has been very pro¬ 
ductive and is still actively worked. The third cross vein is the Wilson, which 
strikes N. 35° E. and is not known to intersect the Isabella. The fourth and fifth are 
the Klondike and Campbell veins, striking respectively due north and N. 30° E., 
both known only at the intersection with the Isabella vein. It is interesting to note 
that these veins all converge toward a point 900 feet northeast of the Buena Vista 
incline. 

EMPIRE NO. 2 VEIN. 

/ 

PRODUCTION AND DEVELOPMENT. 

This vein is partly on Isabella, partly on Empire State ground; it also cuts 
through the northern part of the Pharmacist claim. The name Emma No. 2 is 


394 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


sometimes applied to it. It will be more convenient to describe the deposit as a 
whole rather than each property separately. It has not been possible to ascertain 
the total production, but it is probably not far from $200,000. 

The developments comprise three shafts, named the Edwards, Saunders, and 
Murphy, the last two GOO feet apart and respectively 475 and 450 feet deep, surface 
elevations ranging from 10,470 to 10,516 feet. In addition levels 10 and 11 of the 
Isabella have opened the vein at depths of 725 and 840 feet below the surface. There 
are probably 4,000 feet of drifts and crosscuts. 

GEOLOGICAL FEATURES. 

The croppings are near the contact of breccia and the mass of latite-phonolite 
which farther south, at the Buena Vista incline and the Lee shaft, narrows to 
dike-like proportions. The western part of the outcrop is in latite-phonolite. 
The old workings of the Murphy and Saunders shafts were not visited, but on 
level 10 of the Isabella a large mass of dense phonolite, not known on the surface, 
has been exposed. It is probably one of those flat intrusive bodies so common in 
this district. The phonolite begins a short distance north of the big stope at the 
intersection with the Buena Vista vein and continues for several hundred feet to 
the end of the drift, about halfway between the projection of the Saunders and 
Edwards shafts. A crosscut south connecting with an upraise to the Wrockloff 
workings passes into breccia 200 feet from the vein. 

The same body of phonolite appears on level 11, where the impoverished 
vein at the crossing with the Buena Vista is in this rock. Phonolite appears again 
on this leve 1 for 200 feet east of the projection of Saunders shaft. Another mass 
of phonolite of more dike-like form was noted on the same level 1,000 feet from 
the Buena Vista intersection, where the drift leaves Empire No. 2 vein and turns 
into a south crosscut. A basic dike, probably the Burns dike, here crosses the 
vein and is locally contained in phonolite. 

The Pinto dike is crosscut 150 feet east of the Burns dike. Both have been 
followed for some distance. At the intersection with the Empire No. 2 vein the 
Pinto dike has been faulted 10 feet, the southern part of it being thrown to the east. 

The appearance of gneissoid granite on level 11 is of interest, as no older rocks 
appear on the surface above. The exact point where the Emma vein enters the 
granite on level 11 is 1,400 feet N. 80° W. from the Buena Vista incline, while on 
the surface it is a full half mile to the nearest outcrop of older rocks. For some 
distance back of the contact the breccia contains much granite; the contact itself 
is fairly sharp and stands very steep; the granitic rock is a somewhat sheared and 
gneissoid Pikes Peak granite, with large crushed orthoclase crystals. It is not ' 
brecciated like the isolated, area on the west side of Bull Hill. The same rock 
continues for 400 feet west side of the contact to the end of the drift, and is said 
by Mr. L. S. Grant to continue 400 feet farther to the end of a south crosscut, 
which, however, it was not possible to enter. 

THE VEIN. 

As stated above, the Empire No. 2 vein strikes N. 78° W. and has been fol¬ 
lowed for 1,200 feet on one of the upper levels, as well as on Isabella level 11. The 
dip is very steep to the north; either it is somewhat irregular or there exist on 


I 


\ 


MINES BETWEEN ALTMAN AND GOLDFIELD. 395 

several levels fissures branching from the main one. Intersections with the Buena 
Vista vein at its extreme northwest end, where it is not very well defined, have 
been exposed on Isabella levels 5, 9, 10, and 11. The vein is a narrow sheeted 
zone, whether in breccia, phonolite, or granite. In the breccia near the Buena Vista 
vein it widens in places to 40 feet, but is ordinarily only 2 to 4 feet in width. In 
the fresh phonolite on level 11 it consists only of one central and three lateral 
seams filled with a little crushed quartz and tetrahedrite. Partial oxidation 
continues to level 11, though tellurides prevail in the ore on both 10 and 11. Tetra¬ 
hedrite occurs in places either alone, as mentioned, or associated with calaverite; 
for instance, at the small stope on level 10 below Saunders shaft. 

ORE SHOOTS. 

The vein contains two shoots near the surface and at least two on levels 10 
and 11. The Murphy shoot, 100 feet long and pitching steeply west, reached a 
point 350 feet below the surface. The Saunders shoot had about the same hori¬ 
zontal length and pitch, but pinched 200 feet below .the surface; it yielded $40,000. 
On levels 9 and 10 a very rich shoot was found at or just east of the intersection 
with the Buena Vista vein; its length is 100 feet, and the greatest width 40 feet; 
on level 11 it had pinched in a mass of phonolite. A small body of payable ore 
was reached on level 10 below the projection of the Saunders shaft; still another 
kidney of ore was taken out on level 11 and just below it, in granite, 500 feet west 
of the Saunders shaft. 

To sum up, the shoots on this vein pitch steeply west and have an elongated 
form. The big shoot on levels 9 and 10 is clearly dependent on the intersection 
with the Buena Vista, itself locally unproductive, at a point above a mass of dense 
phonolite. The Saunders shoot lies directly east of the Pinto basalt dike. No 
law was recognized governing the position of the other shoots. 

PHARMACIST VEIN. 

The Pharmacist vein was one of those worked in early times, and a description 
of it may be found on page 194 of Penrose’s report. The vein is continuous for 
1,000 feet from the Buena Vista vein, which it intersects in its lower levels, to the 
faulted crossing of the Zenobia, a short distance west of which it seems to die out. 
On the surface the country rock is chiefly breccia, but in depth the vein at many 
places enters the Altman area of latite-phonolite. The strike is northeasterly; the 
dip averages 60° NW. Ordinarily the vein is a normal sheeted zone containing 
tellurides and quartz. There is much fluorite in the eastern part, while on the 
western side this mineral is nearly absent. Instead, open spaces filled with smoky 
comb quartz prevail. Several shoots occur, chiefly pitching steeply eastward, 
while on the Empire No. 2 westward pitch is the rule. Most of them seem to be 
connected with intersections of other veins, and one occurs at the intersection 
with the Pinto basalt dike. 

EMPIRE STATE MINE. 

The Empire State Gold Mining Company controls the eastern part of the 
Pharmacist and Empire No. 2 veins near their intersection with the Buena Vista. 
The production is at least $600,000, of which $300,000 is stated to have been taken 
out from the big stopes at the intersection just mentioned. 


396 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

The developments comprise the Empire State or Orphan shaft, which connects 
with level 11 of the Isabella (elevation 9,650 feet), called 7 of the Empire State, 
the elevation of the collar being about 10,550 feet; and the Maloney shaft, located 
300 feet farther south and 400 feet deep. Drifts and crosscuts probably add up 
to 4,000 feet. The workings on the Empire No. 2 vein have already been described. 

Both shafts are in breccia, as are the workings on lower levels near the Buena 
Vista vein, but on the western side of the crosscut from the Maloney shaft the 
drifts soon run into latite-phonolite through an indistinct contact. In one of 
the stopes 30 feet above level 4 the vein has a sharply defined central seam of 
fluorite, 2 inches wide, with several smaller seams on each side, and breaks with 
fairly well-defined foot and hanging walls. Twenty feet southwest from this 
place the same width is shown, hut the vein consists of twelve very narrow veinlets 
of fluorite, with occasional small quartz vugs. On level 10 of the Isabella, at the 
east end of the stope, the vein shows a well-defined seam surrounded by silicified 
and pyritic breccia, gradually changing to normal rock within 1 foot on each side 
of the vein. 

The principal shoot worked from the Maloney shaft appears to begin in Pinto 
ground, it is said at the intersection with the so-called Harrington vein, which 
was not, however, identified at greater depth. It pitches steeply eastward down 
to level 4; the maximum length is 200 feet. Probably the same shoot is found 
again on levels 5, 6, and 7 of the Orphan shaft, corresponding to 9, 10, and 11 
of the Isabella mine, and lies chiefly on the west side of the Buena Vista vein, 
though on level 10 the stopes extend 30 feet north of it. Between level 9 of the 
Isabella and level 5 of the Maloney shafts 200 feet of backs should exist if the 
shoot really is continuous. 

PINTO MINE. 

INTRODUCTION. 

The Pinto mine is situated on the saddle between Bull Cliff and Bull Hill, just 
north of the main street of Altman. It is owned by the Free Coinage Gold Minins 

o o 

Company. The production of the mine has been close to 81,500,000. The workings 
consist of a 575-foot shaft and about 5,500 feet of drifting and crosscutting. The 
elevation of the shaft collar is about 10,625 feet. 

GEOLOGICAL FEATL'RES. 

The principal rock of the mine is latite-phonolite. About 500 feet east-south¬ 
east of the shaft, on the 350-foot level, breccia begins and continues to the end of 
the workings. Three basaltic dikes are encountered in the mine. A large dike, 10 
to 20 feet wide, nearly vertical and with an east-northeast course, is cut in two 
places south of the shaft on the fifth or 550-foot level. It corresponds in direction, 
and in appearance also, with the large dike which can be traced on the surface from 
the Eagle mine to the Isabella mine. It may be called the Isabella dike. Two 
hundred and fifty feet south of the shaft the same drift crosses a second dike, 4 to 
7 feet wide, which strikes N. 25° W. and is practically vertical. This is known as 
the Pinto dike. It is characterized by the presence of brownish-black mica, and is 


MIXES BETWEEN ALTMAN AND GOLDFIELD. 


397 


in most places considerably decomposed. The Isabella dike is seen to cut directly 
through the Pinto dike, and no evidence of faulting could be found. The latter 
dike has been opened in ail levels. The third basalt ic dike, known as the Harrington 
vein, is best seen in the southeast crosscut on level 5, about 150 feet from the shaft. 
It strikes X. 10° W. and dips steeply to the cast. Basalt does not occur throughout 
the fissure, but alternately pinches out and comes in, everywhere much decomposed. 
The Harrington vein intersects the Pharmacist on several levels up to the 100-foot 
level. 

VEIN SYSTEMS. 

The principal vein of the mine is the Pharmacist vein. Its course is N. 60° E. 
and it dips on an average 62° NE. The shaft was sunk on the apex ot this vein, 
and at the various levels crosscuts have been run to the north to reach it. So much 
stoping has been done that the vein can be examined in only a few places. On 
level 2 to the east of the crosscut it appears as a narrow crack, sometimes opening 
into small lenticular vugs holding quartz. The country rock is hard latite-phonolite, 
very little oxidized except close to the fissure. In places the Assuring is not con¬ 
fined to a single point, but spreads out into a zone 2 to 3 feet wide. 

The Pinto basalt dike, which is itself of economic importance, is cut by this 
vein, and the Harrington vein or dike, which is elsewhere valueless, influences the 
richness of the ore at its intersection with the Pharmacist vein. The crosscut to 
the southeast on the 550-foot level reaches the Wilson vein 650 feet from the shaft. 
This vein consists of a series of parallel seams in silicified breccia, not much oxidized. 
It carries no ore on this level. Its course is about N. 35° E., and it dips very sharply 
to the northwest. Near the crosscut it is intersected by a sheeted zone which runs 
north-northwest and gives low-grade assays. The drift on the Wilson vein should 
cut the Pinto basalt dike about 750 feet from the shaft, but the dike apparently 
breaks up, for, though fragments of basalt are found about where the dike ought 
to be, no regular^ defined body of that rock is encountered. 

The Pharmacist vein carries values principally as rusty gold, but with here 
and there patches of tellurides in the crevices which make up the vein. The screened 
and sorted ore averaged about $40 per ton where mined, but in places it was of too 
low grade to be worked. The vein is stoped practically continuously from 250 feet 
down to 550 feet from the surface across the property. At the intersection of the 
Harrington and Pharmacist veins an irregular ore shoot 5 to 20 feet in diameter, 
was stoped from above the 100-foot level to the 350-foot level, at which point the 
shoot passed into Empire State ground. The average value of the ore from this 
shoot was 4 ounces. Where the Pharmacist vein crosses the Pinto dike occurred 
one of the rich ore shoots of the camp. The values were largely in the basalt and 
consisted of both tellurides and derived rusty gold, while the Pharmacist vein and 
the mineralized country rock near the dike were completely oxidized. The ore 
was shipped as mined, and gave returns of 7 to 8 ounces. This rich ore occurred 
in a body with a roughly circular horizontal cross section 6 to 15 feet in diameter, 
and reached from the surface to where it left the Pinto ground, 90 feet below the 
550-foot level. At this point the shoot was impoverished. 

On the Pinto dike ore occurred on level 2, 100 feet south of the Pharmacist 
vein. A pay streak 1 foot wide on the west side of the dike in the soft decomposed 
13001— No. 54—06-27 


398 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


basalt gave shipments of 2 to 3 ounce ore. A stope, 75 feet above and 60 feet below 
the level, lias been made along the dike for 70 feet. At the south end the dike is 
cut off by a fault whose direction and displacement are not shown by the develop¬ 
ments. On level 5 are two small stopes on the Pinto dike which gave $20 to $30 
ore. A stereogram of the ore bodies of the Pinto mine is shown in fig. 18 (p. 211). 

BURNS MINE. 

The Burns mine, on the Burns claim, is situated in the western part of the town 
of Altman, between the Pinto and the Pharmacist mines. It is the property of the 
Acacia Gold Mining Company. The total production probably exceeds $200,000. 
Dividends were paid in 1903. The workings consist of a vertical shaft 350 feet 
deep and a 400-foot incline winze from level 4, 350 feet below the surface. Drifts 
and crosscuts at seven levels make the total development about 3,500 feet. The 
elevation of the shaft collar is about 10,625 feet. 

So far as could be determined, latite-phonolite is the only rock encountered 
in the underground workings, though breccia appears on the surface. The Burns 
basalt dike has a course of N. 35° W. and dips steeply to the northeast. It is cut 
on all levels. 

The Pharmacist vein outcrops about 120 feet southeast of the shaft,.which it 
crosses at about level 3. The vein faults the Burns dike, the northern part of the 
dike being displaced 5 to 12 feet to the east wherever examined. 

The Pharmacist vein is a brecciated, partially oxidized zone from a few inches 
to 8 feet wide. On levels 1 and 2 it shows narrow strips of white kaolin and bands 
of manganese. On level 4 the vein is much brecciated and holds a little fluorite, 
quartz, and opal. On level 6 vug holes with crystallized smoky quartz and fluorite 
and seams of kaolin are numerous, while for some distance southwest of the winze 
a 7-inch band of fluorite and quartz occupies the center of the vein. 

The values occur chiefly in the joints and crevices between the brecciated 
fragments. In general, the tellurides have been oxidized to rusty gold, but in 
places they remain fresh. The values vary considerably. Where work is now 
being done, between levels 1 and 3, about one-half of the rock broken is saved and 
averages about $60 per ton. 

An ore shoot began at the surface southeast of the shaft and went down to 
level 2, branching at level 1. Near the surface it is 150 feet long. At level 2 each 
branch is about 50 feet long. Work is now being done below level 2, on the north¬ 
east branch. A little stoping has been done on level 4, just north of the shaft. At 
the east side of the claim a stope averaging 70 feet long and varying from 3 to 10 
feet wide reaches from 125 feet above level 4 down to level 7. It connects with 
the Pinto stope on the same vein. A large, irregular stope, 200 feet long and aver¬ 
aging 150 feet along the dip of the vein, runs from just below level 4 down nearly 
to level 6. It connects on the west with a stope in Pharmacist ground. A smaller 
stope from level 6 goes down below level 7 along the winze. 

A little ore has been taken from the Burns dike on levels 5 and 6 south of the 
Pharmacist vein. The dike seems to have no special effect on values. 


MINES BETWEEN ALTMAN AND GOLDFIELD. 


399 


WROCKLOFF MINE. 

The Wrockloff mine, situated on the north end of the Burns claim, is also the 
property of the Acacia Gold Mining Company. The production could not be learned, 
but it has been considerable. A shaft about 750 feet deep and 2,500 feet of levels 
comprise the underground development. But little work is being done at present. 
The elevation of the shaft collar is about 10,550 feet. 

The workings are mostly in breccia made up largely of latite-phonolite frag¬ 
ments. Fifty feet southeast of the shaft on level 2 the poorly defined contact with 
latite-phonolite is seen. Both the Pinto and Burns dikes are opened in the mine. 
The former splits and branches and breaks up between levels 1 and 6. On it occur 
the principal workings of the mine. On levels 1 and 2 it is 4 to 6 feet wide, nearly 
vertical, and considerably decomposed. A cross vein which strikes S. 25° W. and 
dips 50° NW. is seen on level 2 about 100 feet north of the shaft. It is a narrow 
fissure partially filled with quartz, and carries a little fluorite and patches of kaolin. 
Three levels are opened on it from the Lyons shaft, situated 150 feet north-northeast 
from the Wrockloff shaft. 

At the intersection of this vein and the Pinto dike an ore shoot begins 25 feet 
above level 1, at a point 30 feet north of the shaft, and continues to 20 feet below 
level 4. The values are in general confined to the seams in and at the edges of the 
basalt, but above level 2 the surrounding latite-phonolite is traversed by minute 
seams parallel to the dike, which silicify the country rock and make it ore for several 
feet on each side of the dike in the neighborhood of the cross vein. The values 
decreased below level 4, and the ore soon gave out. This ore shoot was on the east 
branch of the Pinto dike. 

From level 4 to level 6 a body of ore GO feet long was taken out along the Pinto 
dike, which he^e pitches very steeply to the west. This stope is 200 feet northwest 
of the shaft, and it is said that there is no cross vein. 

On level 6 a considerable body of ore was taken out along the Pharmacist vein 
(below the Burns workings) at the point where it crosses the Burns dike. On level S 
(the bottom level) a crosscut was extended to the dike and to the Pharmacist vein 
below the deepest workings from the Burns shaft. 

v • 

PHARMACIST MINE. 

INTRODUCTION. 

The Pharmacist mine, on the claim of that name, is situated at the west end 
of the town of Altman and is owned by the Pharmacist Consolidated Mining Com¬ 
pany. One of the earliest mines to be opened on Bull Hill, it attracted much 
attention by being the first to declare a dividend. The production up to January 
1, 1900, was $650,000, and of that amount $84,000 has been paid in dividends. 
Only small amounts have been produced since that date. 

The underground workings consist of an incline shaft 650 feet long, with eleven 
levels about 50 feet apart, and a vertical shaft about 600 feet deep, with six levels, 
the collar elevation being about 10,625 feet. Level 5 of the vertical shaft corre¬ 
sponds to level 10 of the incline. Connection with the Zenobia mine is established 


400 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


by level 2 of the vertical shaft, corresponding to level 5 of the Zenobia incline. 
The total development is about 6,300 feet. The property is worked on a small 
scale by lessees. 

Latite-phonolite is the only rock seen in the mine, though breccia appears in 
the shallow pits at the surface. 

VEIN SYSTEMS. 

The Pharmacist vein here strikes N. 55° E. and dips about 60° NW. A vein 
with parallel strike, but steeper dip, is seen on level 1 of the vertical shaft, about 
150 feet northwest of the Pharmacist vein. A third vein of about the same direc¬ 
tion, but nearly vertical, occurs between levels 1 and 2, 150 feet north of the vertical 
shaft. These three form a general northeast-southwest system. The Zenobia vein, 
at the point where it enters the Pharmacist claim, has a north-northeast course, 
but soon changes to a practically north-south course, which it retains in most 
of the Pharmacist workings. It dips 70° to 80°. Another north-south vein, 
approximately vertical,, crosses the Pharmacist vein at level 4 of the incline, near 
the shaft, and what is probably the same vein is encountered 80 feet southeast 
of the vertical shaft on level 1. 

CHARACTER AND OCCURRENCE OF THE ORE. 

The ore from the Pharmacist vein is an oxidized latite-phonolite, more or less 
impregnated with silica, and holding many little quartz seams, with vugs partially 
filled with crystallized smoky quartz. The values occur in the seams as rusty gold 
derived from tellurides. The vein is said to have been stoped practically contin¬ 
uously across the claim from the surface down to level 3 of the incline and down 
to level 4 for some distance northeast of the shaft. Work is now being done above 
incline level 4, 100 feet north of the shaft, in what was formerly supposed to be the 
hanging wall of the vein. The oxidized quartz-bearing portion of the vein is low 
grade at this point, but parallel fissures in the unoxidized, partially silicified latite- 
phonolite toward the hanging wall carry fluorite and sufficient telluride to make the 
value of the screenings about S30 per ton. 

A second and smaller body has been found on the Pharmacist vein between 
levels 5 and 6 of the vertical shaft, near the Burns line. The character of the 
vein and the ore are much the same as in the body described above. 

The ore from the Zenobia vein is in most respects similar to that from the 
Pharmacist vein. Quartz is perhaps more abundant, oxidation is a little more 
advanced, and narrow streaks of kaolin are frequently seen. Unoxidized fluorite- 
telluride ore is also met usually along the foot wall and outside of the zone of quartz 
doposition. The values in this vein also vary considerably, some of the ore being of 
high grade. A stope on this vein reaches from a considerable distance above level 
1 of the vertical shaft down nearly to level 2. It begins just north of the shaft and 
is 150 feet long and 4 to 12 feet wide. The values and width of the ore are greatest 
near the shaft on level 1, where a north-south vein, nearly vertical, which is itself 
stoped south of the shaft, joins the Zenobia vein. Another rich bunch of ore occurred 
near the north end of the stope, between levels 1 and 2, where the vein appeared to 
branch again. The best values were found in the east branch, but just at the fork 


MINES BETWEEN ALTMAN AND GOLDFIELD. 


401 


a northeast-southwest vertical fissure came in and increased the value and size of 
the ore body. 

A second ore shoot on the Zenobia vein occurs on level 2 from the main shaft, 
where a stope has been made from a point west of the shaft 60 feet to the Zenobia 
line, both above and below the level. Both rusty gold and tellurides were found 
here, and some pockets were very rich. 

A body of ore of good grade was encountered about 80 feet southeast of the 
vertical shaft on level 1. A poorly defined vein of the northeast-southwest system 
is here cut by a north-south series of vertical fractures. The rock is unoxidized, 
and silicified along the openings. Carbonates are common in the seams and are 
as ociated with tellurides. A chamber 20 by 20 feet, 30 feet high, was stoped at 
this intersection, and the screenings were shipped. 

ZENOBIA MINE. 

The Zenobia mine belongs to Stratton’s estate and occupies the northeasterly 
projection of the large area on Bull Hill, owned by this company. It was one of 
the earliest producers of the camp; its output is stated to have been $140,863. 
A few years ago W. S. Stratton reopened the mine, sinking a vertical shaft 500 
feet deep. The explorations were not very successful, and in 1904 the mine was 
worked only on a small scale by lessee. 

The developments comprise an incline, now abandoned, with seven levels, 
and located 225 feet southwest of the Pharmacist incline; also a new veritcal 
shaft 527 feet deep, with four levels, 215, 315, 415, and 515 feet below the collar, 
which has an approximate elevation of 10,675 feet. Level 4 is about 100 feet below 
level 7 of the old incline. The total length of drifts and crosscuts is 4,000 feet. 

The few exposures visible on the surface indicate breccia, but in the upper 
levels latite-phonolite is the dominant rock. In levels 1 and 2 of the vertical 
shaft only latite-phonolite is exposed, while level 4 shows much breccia, chiefly 
consi ting of fragments of latite-phonolite. Abundant granitic material is also 
contained in the rock in the northwest crosscut. 

The veins worked are the Pharmacist, opened chiefly on the northeast side 
of the incline close to the Pharmacist claim, and the Zenobia, which is developed 
chiefly on the southwestern side of the incline. The Pharmacist vein here strikes 
N. 50° to 65° E. and dips 60 NW., while the Zenobia strikes from N. 20° E. to 
almost north-south, the dip varying from 60° to 80°. These two veins intersect 
along a line with northerly dip and are exposed down to level 5 of the incline. A 
fault takes place at the intersection, the eastern part of the Pharmacist vein being 
thrown from 10 to 20 feet to the south. West of the intersection the Pharmacist 
vein is not well defined. Development on the 515-foot level has disclosed three 
veins within 175 feet, which strike approximately like the Zenobia and which may 
be branches of that vein. 

Both veins show unusually large amounts of smoky quartz, much of it well 
crystallized, occurring in fissures and in cavities formed by solution. Little fluorite 
is present, and the ore is oxidized to the deepest level. Large amounts of yellow 
opaline silica are present as the latest vein mineral, and at many points cover druses 


402 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


of quartz as confused masses of tubular rods. The rock near the vein contains much 
fine-grained pyrite, and is said to carry values in places. 

The veins exposed on levels 4 are oxidized sheeted zones with large vugs filled 
with smoky quartz. Much of the surrounding rock shows distinct silicification, 
and opal is probably being deposited at the present time. 

The ore shoot is confined chiefly to the Pharmacist vein, east of the inter¬ 
section, up to the Pharmacist line, though some ore wa§ also mined on the upper 
levels of the Zenobia vein. Very little stoping has been done below level 5 on the 
incline; a small shoot was, however, found on level 8, 50 feet northeast of the foot 
of the incline. The veins exposed on level 4 of the vertical shaft contain poor 
values, though reports indicate that subsequent prospecting has developed ore of 
better tenor. 

MERCER MINE. 

The Mercer mine is located on the Wilson claim, just south of the main street 
of Altman. It lies between the Pinto and the Deadwood mines and is owned by 
the Free Coinage Company, though worked under lease to Mr. D. N. Mercer. The 
production is estimated at $200,000. The underground development consists of an 
incline shaft 350 feet deep and about 600 feet of drifts. The workings are entirely 
in latite-phonolite, though the 550-foot level of the Pinto mine, directly beneath, 
is in breccia. 

The shaft is sunk on the Wilson vein, which strikes N. 35° E. and dips very 
steeply to the northwest, with local variations. A crosscut to the southeast on 
the 50-foot level discloses a vein of practically parallel strike 15 feet from the Wil¬ 
son vein and dipping toward it. The two veins come together just above the 120- 
foot level, the junction being approximately horizontal. The two veins appear to 
merge into one and to so continue to the bottom of the workings. 

A small bunch of ore was found on the main Wilson vein above the junction, 
the screened ore of which yielded 10 ounces per ton. No ore has been found on the 
branch vein. At the junction of the two veins a good body of ore was found. The 
united vein consisted of a 7-inch band of fluorite and many narrow seams in the 
oxidized latite-phonolite, all carrying rusty gold and a very little telluride. The 
fluorite decreases below and finally gives out, but the values continue. Near the 
junction some of the ore held gray copper and contained up to 15 ounces of silver 
per ton, but very little tetrahedrite was found below this point. About 10 per 
cent of the rock broken passed through a one-fourth inch screen, giving values of 
13 to 62 ounces per ton. One-third of the total passed through a 1-inch screen 
and ran from 14 to 5 ounces per ton. The stope averages 4 feet wide, 180 feet long, 
and 150 feet deep and continues to the line between the Mercer and Murphy mines. 
The deepest point is on the 300-foot level near this line, and the 550-foot level of 
the Pinto failed to find ore. In sinking the shaft from the 210- to the 250-foot point 
a rich pocket in the ore shoot was found, which produced $11,000 This entire 
ore shoot was taken out by underhand stoping, as in that way more fines were pro¬ 
duced and a better saving of values effected. 

A small stope is now worked on another ore body above the 250-foot level and 
180 feet northeast of the shaft. The values here are confined principally to dark, 


MINKS BETWEEN ALTMAN AND GOLDFIELD. 


403 


muddy streaks 1 to 3 inches wide, which occur at one side or the other of the sheeted 
zone. The material is completely oxidized and, when panned, proved to be very 
rich in gold. 

MURPHY MINE. 

The Murphy mine, also owned by the Free Coinage Company, is situated on 
the Wilson claim about 120 feet southwest of the Mercer mine. The production 
was not ascertained, but has been considerable. The workings consist of a 350- 
foot incline shaft and 7,800 feet of drifting. 

The Wilson vein continues from the Mercer into Murphy ground and is the 
principal vein of the mine. Its character is much the same as in the Mercer, but 
no fluorite was seen. Another vein, practically vertical, of irregular strike, but 
averaging about S. 20° W., branches off on the east side of the main vein. There 
seems to be no crossing, and to the north of the point where the veins come together 
the two seem to unite as one vein. The junction is about 60 feet southwest of the 
shaft at the surface and pitches so that it is about an equal distance northeast at ♦ 
the bottom, becoming more nearly vertical with increasing depth. 

The ore occurs in the seams and fissures and is almost wholly oxidized. By 
screening and sorting about one-fifth of the rock broken is saved as ore and runs 
$30 to $300 per ton. Underhand stoping improves the values of the ore saved, as 
in the Mercer mine. Ore on the Wilson vein was stoped from the Mercer line to a 
point where the values quickly decrease, 15 to 30 feet southwest of the junction. 
The stope reaches from the surface to the 350-foot level, where the shoot practically 
ends. Ore along the junction of the veins was better than elsewhere. The branch 
vein has been stoped 100 feet from the junction from about the 300-foot level up 
almost to the 70-foot level, and work is being done in good ore higher up. The 
occurrence and amount of the valuable minerals are practically the same as in the 
main vein. 

Whether or not there is any relation between this branch vein and the one 
which branches from the Wilson vein in the Mercer workings it was impossible to 
determine. 

PUEBLO MINE. 

The Pueblo mine is located on the claim of the same name and lies well up on 
the western slope of Bull Cliff. It is the property of the Free Coinage Company 
and is being worked under lease. The production of the mine is not large. The 
underground workings consist of a 100-foot incline shaft and two levels represent¬ 
ing about 150 feet of drifting. 

The shaft is sunk on a vein striking N. 55° W. and dipping about 80° NE. It 
is 2 feet wide and is oxidized and brecciated. On account of the decomposition of 
the country rock its character could not be determined. The 50-foot level follows 
the vein on both sides of the shaft. A stope 15 to 20 feet high and 75 feet long 
above the level yielded $15 to $40 values in rusty gold after screening and sorting. 
On the 100-foot level the northwest-southeast vein is crossed 15 feet northwest of 
the shaft by a north-south vein dipping 45° W. Stoping is being done along both 
veins, and oxidized ore running $20 to $40 is being shipped. 


404 GEOLOGY AHD GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

■ 

WACU WETA MINE. 

I 

The Maroon Tunnel Company owns the mine which is situated on the Wacu 
Weta claim, on the northwest slope of Bull Cliff. It is being worked under lease. 
The developments consist of an incline shaft 308 feet deep and about 500 feet of 
drifting and crosscutting. The production of the mine is not large. 

The rock at the surface is the Bull Cliff phonolite, but the shaft quickly passes 
into latite-phonolite, which continues to the bottom. About 80 feet southeast 
from the bottom of the shaft a sharply defined, vertical, apparently intrusive con¬ 
tact of latite-phonolite and breccia is exposed in a crosscut. 

The shaft is sunk on a sheeted zone dipping about 80° SE. The vein varies 
from 1 to 4 feet in width and is not much oxidized. It is said to be the Klondike 
vein of the Isabella mine, but this seems very questionable. An ore shoot averag¬ 
ing 25 feet long and 4 feet wide was stoped from the surface near the shaft to the 
second or 150-foot level; it pitched steeply to the southwest, but did not continue 
below level 2. On level 4, at a depth of 300 feet, a small bunch of ore was encoun¬ 
tered 30 feet south of the shaft, but gave out at an irregular mass of dense phonolite. 
A 1-inch manganese seam enters the phonolite and is seen to turn abruptly toward 
the east. In 10 feet it crosses a ,3-inch seam of soft oxidized material, and at the 
junction a few carloads of $20 to $40 ore were mined. 

DEADWOOD MINE. 

PRODUCTION AND DEVELOPMENT. 

The New Zealand Mining Company, controlled by the Woods Investment Com¬ 
pany, owns the Deadwood claim, on which the Deadwood mine is situated. It lies 
south of the saddle between Bull Hill and Bull Cliff. The combined production of 
the Deadwood and Trachyte mines probably does not exceed $200,000. A num¬ 
ber of shafts explore the country rock near'the surface, and the main shaft, which 
is about 700 feet deep, has seven levels; the elevation of the collar is 10,545 feet. 
Drifts and crosscuts aggregate 7,000 feet. Only the first three levels could be 
examined. 

GEOLOGICAL FEATURES. 

The shaft and main workings of the mine are in a lobe of breccia reaching down 
from the north. The surrounding latite-phonolite is penetrated in several places. 
The contact is nowhere sharp, the indication being that the breccia has been locally 
derived from the massive rock. This contact is seen on level 1, 225 feet X. 40° W. 
frcm the shaft. It is in approximately the same relative position on level 3. On 
the same level, about 300 feet northwest from the shaft, the end of the crosscut just 
enters a soft, partially oxidized breccia, of which no indication was found on the 
surface. Latite-phonolite is again cut near the end of the drift on level 3, about 
250 feet south of the shaft. A small mass of dense phonolite, which is probably a 
northwesterly trending dike, was observed in two places on level 1, 200 feet north¬ 
west of the shaft, but not elsewhere. 


MINES BETWEEN ALTMAN AND GOLDFIELD. 


405 


VEIN SYSTEMS. 

Two definite systems of fissures occur in the mine. One strikes N. 20°-25° W. 
and has varying nearly vertical dips. The other has a course about N. 75°-80° E. 
and dips to the south at a high angle. The north-northwest system is represented 
by a number of veins of varying persistency and importance, while the east-west 
system consists of one well-defined vein. This vein, which lies about 60 feet north 
of the shaft on level 1, is about 3 feet wide and nearly vertical. It consists of a 
number of parallel fractures in dense, partially oxidized and silicified breccia. One 
hundred feet northwest of the shaft it cuts one of the principal veins of the north- 
northwest system, and on level 1 appears to fault it, the northern part being thrown 
about 10 feet to the west. There is no evidence of faulting at the corresponding 
points on levels 2 and 3. The veins of the north-northwest system are in general of 
similar character, but vein brecciation has often occurred, oxidation is frequently 
greater, and fluorite is a common vein mineral. 

The east-west vein has been stoped from the surface down to 40 feet below level 
1, about 250 feet long, the values occurring in the seams and fissures as tellurides 
and as rusty gold derived from them by oxidation. The screenings, which amounted 
to about one-third of the total vein matter, ran $60 per ton. At the point where 
this vein faults the north-northwest vein a stope 20 by 20 feet has been made in ore 
that is said to have been of very good grade. How far above and below the level 
this rich part extended was not ascertained. On the east side of the north-north- 
west vein the stope on the east vein is being continued down to level 2. On the 
west side it has gone down at least a considerable distance below level 3. 

The north-northwest vein, which is faulted by the east-west vein, is similar to 
the latter except that it is a little more oxidized. It passes about 40 feet west of the 
shaft on level 1 and is approximately vertical. Small bunches of ore have been 
taken from it just west of the shaft and 70 feet south of the shaft. This may be the 
same vein which is being worked 150 feet south of the shaft on level 3. The latter 
vein, which is 2 feet wide and dips steeply to the east, is much brecciated, and the 
oxidized fragments are held by a filling of purple fluorite. Screenings carrying 
20 ounces to the ton make up about one-fifth of the total ore; they contain rust}' 
gold, with occasional tellurides. A mineral which is probably tetrahedrite is some¬ 
times found with the telluride. 

A vein of the north-northwest system dipping steeply to the west is reached 
about 250 feet north of the shaft on level 1. It has been stoped extensively, but is 
not encountered again on other levels. 

Two other veins of this system have been drifted on for a short distance 200 
feet northwest of the shaft on level 3. One is practically vertical; the other, 30 
feet to the west, dips at a high angle to the east. A few small bunches of ore have 
been taken from these veins. Much ore is also said to have been extracted from a 
flat vein near the surface. 

On the whole the occurrence of the ore seems to be connected with the inter¬ 
section of the two vein systems. 


406 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

9 

TRACHYTE MINE. 

The Trachyte mine, on the claim of the same name, lies 500 feet southeast of 
the Deadwood, is also the property of the New Zealand Mining Company. It is 
explored by a shaft 400 feet deep and four levels, representing a total development 
of 2,500 to 3,000 feet. The elevation of the collar is 10,462 feet. The country rock 
is latite-phonolite, oxidized in places. The basalt dike from Deadwood No. 2 passes 
not far west of the shaft. ' 

Owing to accumulation of ice in the shaft below level 1, only that level was 
entered. A crosscut 120 feet to the north discloses a vein with a trend slightly 
south of east, and dipping about 65° N. It has been stoped from close to the sur¬ 
face down to at least level 2, for a distance of 200 to 300 feet along the vein. The 
character of the vein matter could not be seen. 

PEARL MINE. , 

The Pearl mine is situated between the Trachyte and the Deadwood No. 2, and 
has some workings on the Deadwood No. 2 basalt dike. 

DEADWOOD NO. 2 MINE 

INTRODUCTION. 

Near the south end of the Deadwood claim a shaft has been sunk and work done 
principally by lessees. It is called the Deadwood No. 2 mine, and is estimated to 
have produced $150,000. The shaft is 850 feet deep and has nine levels which rep¬ 
resent about 4,000 feet of drifting and crosscutting. The elevation of the collar is 
10,410 feet. 

GEOLOGICAL FEATURES. 

The shaft and workings are in latite-phonolite. Levels 2 and 9 appear to enter 
breccia 140 feet west of the shaft, but this point could not be definitely determined. 
A 3-foot vertical phonolite dike striking about north and south is exposed on level 
2 about 150 feet west of the shaft. The important geological feature of the mine is 
a basaltic dike cut by the shaft at level 1, having a general course about N. 20° W. 
and dipping on an average 80° W. The dip varies considerably, however, as does 
also the strike. The dike is irregular in width, ranging from 1 to 5 feet, but becomes 
more uniform with depth. On level 1 it appears to branch south of the shaft. The 
drift leaves the dike and soon cuts another approximately parallel dike. On level 2 
a similar occurrence is met with just north of the shaft. Twenty feet north of the 
shaft on level 1 the dike is faulted, the north part being thrown 1 foot to the west. 
A narrow seam with a strike parallel to the dike, but which dips every steeply toward 
the west, branches off from the dike just below level 1. On level 6 this seam, which 
is still at the shaft, carries 6 inches of decomposed basalt. It is cut again on the 
lower levels, where the dip becomes slightly less and the width of basalt increases 
to 15 inches on level 9. The main basalt dike shows a corresponding loss in width 
as the other widens. 


MINES BETWEEN ALTMAN AND GOLDFIELD. 


407 


CHARACTER AND OCCURRENCE OF THE ORE. 

On the first level a northwesterly vein dipping about 75° SW. is reached by a 
northeast crosscut 100 feet from the shaft. It consists of a partially oxidized, 
shattered, and sheeted zone in latite-phonolite. A small bunch of ore was encoun¬ 
tered just above the level. A stope 3 feet wide, 25 feet long, and 15 feet high 
furnished a carload of $15 screenings. What is probably the same vein was explored 
for a short distance on the second level, but showed no ore. 

The principal amount of ore came from the basalt dike. This is everywhere 
very soft and at the sides lies a decomposed, more or less clay-like gouge, which is in 
places oxidized, and which varies in width from a very narrow seam to several inches. 
The values occur in this partly as tellurides and partly as rusty gold. Where the 
values are exceptionally high the near-by basalt and country rock also may constitute 
ore. But since in general the dike was worthless, it was carefully shot down and 
then the soft selvage was picked down and caught on sheets. The process is called 
stripping, and requires no sorting. The value of the material so obtained varied 
considerably, but was always good, the range being $80 to $3,000 per ton. 

ORE SHOOTS. 

Beginning at the surface about 50 feet north of the shaft, on the basalt dike, 
is an ore shoot 130 feet long, which pitches steeply to the south. At level 1 it has 
been stoped 120 feet along the dike, the value of the ore shipped being about $80. 
On level 2 the shoot is 60 feet long and nearly vertical, the pay streak at the side 
of the dike being 1 to 8 inches wide. A small lot of gold-bearing rock too low in 
grade to be profitably worked, was taken out 40 feet south of the shaft on this level. 
On level 3 the shoot has been stoped for 50 feet. Between this and the next level 
the dike flattens considerably, and the ore shoot turns from nearly vertical to a 
much flatter pitch to the south, narrowing up and finally pinching out just before 
reaching the fourth or 400-foot level. Below level 4 the dike steepens again, 
but no ore was found between the fourth and fifth (470-foot) levels. Between the 
470- and 550-foot levels occurred the richest ore in the mine. The pay streak was 
wider and the values better than elsewhere. The ore shipped brought returns of 
$300 to $700 per ton. The stope here was almost 300 feet long. For 120 feet in 
the middle the main values were on the hanging wall, while at each end of the stope 
they were on the foot wall. Where the pay streak crossed the dike at the south a 
triangular body of very rich ore was formed, the screenings from which shipped at 
$1.37 per pound. At the north end, however, only a narrow seam crossed from the 
hanging to the foot wall. Below level 6 the ore was of good grade, hut was confined 
to a narrow strip on the hanging wall, directly under that which occurred on the 
hanging wall above. Between levels 7 and 8, 650 and 750 feet, respectively, from 
the surface, the pay streak was exceedingly narrow. A stope 120 feet long is con¬ 
tinuous with that on the two levels above, and a stope 40 feet long was made about 
50 feet to the north of the main ore. Stoping is in progress upward from level 9 in 
a corresponding position to the main stopes above. The values are contained in a 
soft greenish-black material one-half inch to 3 inches wide, mainly on the foot wall. 
Its value is about $275 per ton. 


408 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


To summarize, there are two principal ore shoots on the basalt dike. One 
begins at the surface 130 feet, pitches steeply to the south, and gradually shortens 
till it pinches out about 385 feet below the surface. This shoot is fairly regular in 
form and the values are pretty evenly distributed through it. The second shoot, 
which is directly below the first, begins at the 470-foot level and has been proved to 
the 850-foot level. It is irregular in form and the values which it carries vary 
greatly in different parts. 

DELMONICO MINE. 

The Delmonico claim, on which the mine is located of the same name, lies on 
the western slope of Bull Cliff, just east of Deadwood. It belongs to the Stratton 
estate and is worked by lessees. The development consists of a shaft 600 feet deep, 
300 feet of which have recently been completed, and three levels at 100-foot inter¬ 
vals. Development in the lower part of the mine is in progress. Drifts and cross¬ 
cuts probably aggregate 2,500 to 3,000 feet. 

The principal rock of the mine is latite-phonolite, but phonolite breccia is 
reached on level 2, 350 feet south of the shaft. Ninety feet south of the shaft on 
this level the basalt dike from the Deadwood No. 2 crosses the north-south drift. 

Only one vein of any importance has been encountered. It has a north-south 
course, dips steeply to the west and lies just east of the shaft. It consists of an 
oxidized and shattered zone 2 to 5 feet wide in latite-phonolite. Fifty feet south 
of the shaft a body of oxidized ore was encountered which was shipped as broken, 
and contained II to 2 ounces per ton. A stope on this ore shoot is 4 to 5 feet wide, 
35 feet long, and 100 feet high. The southern limit of the shoot is the basalt dike, 
which is also being stoped near the vein. This was the only shoot that had been 
found in the mine at the time of visit. 

VINDICATOR RODE SYSTEM. 

The depression between Bull Hill and Bull Cliff contains one of the most 
important and productive lode systems of the camp. While the general country 
rock is breccia showing the usual alteration, there are in this vicinity two large 
intrusive masses, the northern one consisting of latite-phonolite and the southern 
one of syenite. A smaller intrusion of latite-phonolite adjoins the syenite on the 
south near the town of Goldfield. The mining developments show that these are 
not flat masses, but rather deep batholiths extending to the greatest depths yet 
attained. The syenite borders in places with sharp contacts against latite-phonolite, 
while other exposures present all kinds of transitions between the two rocks. There 
are few basic dikes and few phonolite dikes in this vicinity; none of them is of 
economic importance. 

The lode system is traceable for nearly a mile, the individual veins diverging 
slightly northward, as is well shown in the Vindicator and Golden Cycle mines. 
The dip is usually very steep. The following mines, taken from north to south, are 
located on this system: Shurtloff, Findley, Hull City, Lillie, Ahndicator, Christmas, 
and Golden Cycle. All of them are producing mines of importance except the 
Christmas and the Lillie, on which little work is now being done. The total produc¬ 
tion of the system is approximately $10,000,000. 

A depth of 1,500 feet is attained in the Lillie, 1,400 feet in the Findley, 1,200 
feet in the Vindicator, "and 1,000 feet in the Golden Cycle. 


MINES BETWEEN ALTMAN AND GOLDFIELD. 


409 


FINDLEY AND SHURTLOFF MINES. 

PRODUCTION AND DEVELOPMENT. 

The Findley and Shurtloff mines, which are owned by the Findley Gold Mining 
Company, are situated on the southeastern slope of Bull Hill just above the town 
of Independence. On the south the property adjoins the Hull City mine, while the 
Stratton estate holdings lie on the west. The principal production has been during 
the last few years. The output of ore of the Findley mine for the two years previous 
to 1904 was 11,850 tons; during earlier years 5,000 tons were produced. The total 
production of the two mines to April, 1904, approximated $700,000. 

The developments on the Findley consist of a vertical shaft, with collar eleva¬ 
tion of 10,398 feet and depth of 1,387 feet. Fifteen levels are turned, while at station 
16 the vein has not as yet been crosscut. The numbering and elevations of levels 
are shown on fig. 50 (p. 414); the bottom level (15) having attained an elevation of 
9,119 feet. Drifts and crosscuts aggregate about 2 miles in length. The Shurtloff 
shaft is situated 800 feet north-northwest of the Findley, and its collar is 129 feet 
higher; it is 900 feet deep, with ten levels at various intervals down to the 800-foot 
point. Level 10 lies 25 feet above Findley level 9; Findley level 11 extends under¬ 
neath the Shurtloff workings without making connection with them. Drifts and 
crosscuts amount to 4,500 feet. 

GEOLOGICAL FEATURES. 

On the surface in the south end of the property the veins are contained in brec¬ 
cia, though the contact of the Altman area of latite-phonolite is only a few hun¬ 
dred feet distant to the northeast. Near the Shurtloff shaft the veins enter this 
rock and the shaft is said to have passed through over 400 feet of it before entering 
breccia, which continues down to the bottom. The Findley shaft is sunk in breccia. 
A crosscut to the northeast on level 11 reveals a sharp contact with syenite or coarse¬ 
grained latite-phonolite, 130 feet from the shaft; this probably represents the down¬ 
ward continuation of the Altman area. Moreover, though all accessible crosscuts 
from shaft to vein showed breccia, there is certainly latite-phonolite on level 11 for 
several hundred feet south of the shaft and for 600 feet north of the shaft to a point 
just north of the cross vein described below. The same rock is prevalent on level 
14 along the vein, though the crosscut is in breccia, so that it would seem as if there 
existed a dike-like mass of latite-phonolite following the vein, at least on the lower 
levels. Level 15 was not accessible, being covered with water in April, 1904. 

The breccia contains abundant fragments of latite-phonolite, and at the end of 
the east drift on the cross vein 600 feet north of the shaft much granitic material is 
present. Smaller masses of phonolite—dikes and sheets—are found in various parts 
of the mine, but have little practical importance. A small northeasterly trending 
basic dike was cut on level 14, 450 feet south of the shaft. 

A crosscut 1,100 feet long, which extends west-southwest underneath Moun¬ 
tain Beauty ground, reveals only breccia; neither the latite-phonolite nor the two 
basalt dikes seen on the surface were observed here 1,150 feet below the surface. 


410 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 



Fig. 47.—Vein system on level 11, Findley 
mine; elevation 9,525 feet. 


VEINS. 

The two principal veins are the Findley and the 
Shurtloff No. 2, the latter lying 80 feet east of the 
Findley. Both form, together with the Shurtloff 
No. 1 on the adjacent Stratton propert} r , the most 
northerly extension of the 
great Vindicator system of 
linked veins. The Findley 
is the northerly continua¬ 
tion of one of the Hull 
City veins; its strike is 
N. 31° W., which it main¬ 
tains for a distance of 1,000 
feet; its dip, shown on 
fig. 47, is extremely steep to 
the west-southwest. The 
Shurtloff No. 2, striking 
N. 18° W. and also very 
steep, is first noted near 
the cross vein, 600 feet 
north of the Findley shaft, 
and lias been followed for 
500 feet northward to a 
point where it exhibits a 
tendency to split and turn 
to the northwest. Two 
parallel veins have been 
opened for a short dis¬ 
tance, 100 feet east of the 
Shurtloff shaft, and an¬ 
other lies on level 11, 150 
feet west of the Findley 
vein. An important cross 
vein intersects the Findley 
and the Shurtloff on levels 
10 and 11, 600 feet north 
of the Findley shaft; its 
trend is N. 37° E., and its 

dip very steep to the north- Fig. 48.—Cross section of Findley 
West Vein tllrough Findley shaft look¬ 

ing northwest. 

The main veins are nar¬ 
row sheeted zones, usually with one central seam, 
containing vugs coated with dolomite, quartz 
crystals, and tellurides, and several subordinate 
seams on each side, the total width being usually 
less than 3 feet. The rock is, as a rule, almost 




















































MINES BETWEEN ALTMAN AND GOLDFIELD. 


411 


fresh close up to the fractures. There is little fluorite and a very small quantity of 
pyrite, the latter disseminated in the rock. Bunches of molybdenite were found on 
level 13, and a little tetrahedrite on level 14. 

The cross vein contains a central band of fine-grained fluorite, up to 15 inches 
thick, with several parallel seams on each side. While free gold is practically absent 
on the lower levels of the main veins, this cross vein shows some, doubtless due to 
incipient oxidation. At the intersection with the Findley no faulting is visible, 
but the northeasterly trending vein cuts through the former and would thus seem 
to be somewhat more recent. On the other hand, the Shurtloff vein faults or 
deflects the cross vein, the eastern part being thrown 6 feet northward. 

A crosscut to the west-southwest, 1,100 feet long, explores the Mountain Beauty 
ground just south of the Stratton estate holdings, and begins on level 11, 350 feet 
south of the shaft. Two veins were found in the general southern continuation of 
the Pikes Peak or Mineral Hock vein and about 300 feet south of the Lucky Guss 
No. 2 shaft, but which of them represents the vein mentioned is uncertain. Their 
distance from the beginning of the crosscut is 630 and 790 feet. Both veins show 
tellurides on tight seams. 

ORE SHOOTS. 

The shoots of the Findley mine do not appear at the surface. The principal 
ore body begins between the Findley shaft and the Hull City line, about 150 feet 
below the surface, but is rather small and irregular down to a point 500 feet below 
the surface, where it widens to 400 or 500 feet and occupies both sides of the shaft, 
extending to the Hull City line on the south. In the deepest levels it splits into 
two bodies south and north of the crosscut from the shaft; these were stoped on 
level 14 at the time of visit. The greatest width is 6 feet, and, as a rule, only the 
screenings constitute ore. 

North of the cross vein, in Shurtloff ground, the Findley is called the West vein; 
it is here generally poor, but has been stoped for 50 feet some distance above level 8. 
The Shurtloff vein splits near its north end 100 feet north of the shaft of the same 
name, and a branch connects with the Findley. The northwest branch of the vein 
is stoped on level 8 from the fork to the point where it meets the West vein and 
upward for 70 feet. The north-northwest branch is stoped for 50 feet beyond the 
fork. Just at the junction of the two branches is a good body of ore; it begins north 
of the shaft above level 7 and has been stoped down to level 10, 800 feet below the 
surface. From a length of 70 feet at the top it increases to 350 feet at level 10, the 
north end of the stope being about vertical, while the south end pitches south. 
The stope varies in width from 5 to 12 feet. At level 9 the vein consists of two prin¬ 
cipal seams, with minor ones on each side, and the whole width is stoped. The ore 
from this stope is screened and sorted, and one-fifth to one-third is saved. The 
value of the ore shipped is 2 to 2^ ounces. 

The northeasterly trending cross vein, which is probably identical with the 
Wilson vein on Pinto ground, presents some important features. A large body of 
ore, up to 30 feet in width, was found at its intersection with the Findley, 600 feet 
north of the shaft, on Findley levels 10 and 11, 725 and 825 feet below the surface. 
This cross vein carries fair ore all along for 225 feet northeast of its intersection 


412 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


with the Findley; but at the crossing with the Shurtloff vein, which is barren on 
level 11, it proved valueless for 10 feet on each side of the intersection. Near the 
end of the drift on this cross vein values were suddenly cut off by a northwestward- 
trending seam. 

To sum up, no ready explanation can be given for the occurrence of the main 
shoot, while the Shurtloff shoot seems dependent on the split in the vein, and the 
large bod} 7- on the cross vein conditioned by the crossing with the Findley. It is 
remarkable that the next crossing with the Shurtloff should be attended by a decided 
impoverishment. 

HULL CITY MINE. 

PRODUCTION AND DEVELOPMENT. 

The Hull City mine is owned by the Independence Consolidated Mining Com¬ 
pany, and consists of an almost square area of 39 acres, except for two claims of 
Vindicator property which project into it from the southeast. The total produc¬ 
tion approaches $2,000,000, of which $900,193 was extracted up to the end of 1899 
and $999,174 during the three years from January 1 , 1901 to January 1 , 1904. 
During 1904 the mine was worked on a smaller scale by lessees. 

The developments consist of a main vertical shaft 1,265 feet deep, with eleven 
levels turned. The elevation of the collar is 10,279 feet. The levels are somewhat 
irregularly placed, as shown on fig. 54. Level 11 has an elevation of 9,029 feet. 
Six hundred feet to the southeast, near the southern boundary, is the King or 
Vaughn shaft, also known as the Glorieta, with a collar elevation of 10,204 feet 
and a depth of 860 feet. This has twelve levels, the upper ones being close together; 
level 4 corresponds about to main level 1, and level 12 to main level 8. There are 
also many small shafts less than 400 feet in depth. The developments have a 
total length of several miles. On level 11 the crosscut has not yet reached the 
vein. In April, 1904, water stood 1,055 feet below the collar, and the two lowest 
levels were inaccessible. During 1903 the pumps kept the mine dry, raising 300 
gallons a minute. 

GEOLOGICAL FEATURES. 

The principal rock on the surface, as well as on all lower levels, is a normal 
breccia in which latite-phonolite usually predominates. The change to latite- 
phonolite, which occurs both near the Findley line and at the south end of the work¬ 
ings, is gradual. A very prominent dike of latite-phonolite traverses the property 
for a distance of 1,000 feet from the Findley to the Vindicator boundary. Its strike 
is northwest or north-northwest, its width from 9 to 15 feet, and it stands nearly 
vertical. Southward it merges into the latite-phonolite of the Vindicator, while 
northward it seems to disappear shortly before the Findley line is reached. The 
dike is prominently porphyritic by large orthoclase crystals and more nearly 
approaches the trachytes in appearance than most of the latite-phonolites of the 
district. It occurs on all the levels below 3, but as the upper workings are inac¬ 
cessible, its continuation to the surface could not be shown. A crosscut on level 
4 extends 500 feet to the northeast and passes through two dikes of phonolite and 
two of latite-phonolite; at its extreme end it cuts a basic dike. 


MINES BETWEEN ALTMAN AND GOLDFIELD. 


413 


THE VEINS AND THEIR ORE. 

v 

The vein system in this mine is somewhat complicated. The present descrip¬ 
tion follows the views of Mr. F. G. Willis, who some time ago undertook a careful 
geological examination; figs. 49 and 50 illustrate these relations. Near the surface 
a principal vein, pretty well defined and nearly vertical, called the “C” vein, 
seems to pass from the Findley shaft close by the Minnie Bell and Tompkins shaft 
to the main shaft, and thence down to the Vaughn or Glorieta shaft across bv the 
Vindicator No. 2 shaft, a 
total distance of 1,300 feet, 
with a strike of N. 40° W. 

Three or four hundred feet 
below the surface two other 
veins appear on the north¬ 
east side of the shaft, while 
the “C” vein, with more 
decided southwesterly dip, 
crosses the big dike. Another 
vein, called the “D,” fol¬ 
lows the northeastern side 
of this dike. On level 10 
three veins are exposed— 
the Winze vein, the “ D” 
vein, and the “B v vein. 

The “ A” vein is known only 
on levels 3, 4, and 5 (fig. 54). 

The veins show the usual 
structure and consist of sev¬ 
eral tight seams, in places 
separating brecciated mate¬ 
rial, or of a central seam, 
with small vug holes coated 
with quartz and fluorite, 
surrounded by several less 
distinct cracks. Dolomitic 
carbonates and pyrite are 
disseminated through the rock in the vein at many places, also outside of it, and 
crystallized carbonates may often be seen coating the seams. 

The stopes on the “D” vein along the dike on level 4, north of the shaft, 
showed a very much crushed, nonoxidized dark-green breccia, in which much 
replacement by fluorite and pyrite, apparently also by calaverite, has taken place. 
The vein was stoped 2 feet wide and all of the material sacked. The “A” vein 
on this level is 3 feet wide in the pay shoot, with about six parallel and oxidized 
seams. On level 7 veins “C” and “D” lie close together, and “C” appears to 
cross the dike, which contains small streaks of stibnite and galena. The veins are 
partly oxidized on this level. 

13001 — No. 54 -06 - 28 








414 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


The principal ore is calaverite, occurring as usual, coating narrow seams in 
the vein, but also to some extent as replacement. In the lower levels tetrahedrite 

began to appear, especially in the 
“B” or shaft vein, from a point 
850 feet below the collar to the 
bottom. This vein generally as- 
saj^s comparatively high in silver. 
Gold accompanies the tetrahe¬ 
drite, but this particular ore is not 
of high grade. Assays gave, for 
instance, gold, $8; silver, 8.5 oun¬ 
ces; copper, 0.2 per cent. Galena 
occurred in the “C” or Winze 
vein; on level 9 a mass was 
found 1§ feet wide, consisting of 
galena, zinc blende, and pyrites, 
with good values of gold. Simi¬ 
lar ore occurred on the “ D ” vein, 
250 feet south of the shaft. On 
the other hand, the breccia’ close 
to the vein on level 7, at the Vindi¬ 
cator boundary line, contained 
much massive pyrite and zinc 
blende which proved practically 
barren. On' the same level a 
seam with much stibnite oc¬ 
curred. Molybdenite occurs fre¬ 
quently in the ore. Partial oxi¬ 
dation extends at least 850 feet 
below the collar. 


T‘ 

ii 

10800 

IV 

L 11 


<gll 

-I 1 ' 

<ol| 1 
.O' 1 
gill 

•K) 

^ 10000 

S, |J 

Wi// 
0 // 

1 st level 

<77 7 

ndl level 

l i 3 rd level 


1 

§ S' 

4 th level 

Dike, 

mi 111 iiiii riii 

jit:* 

•W ' 

1 V 

J 

l 5 th 

level 

A 

/t 

/ 1 

/ 11 i 

/M 

6 th level 

9500 


vein 

•vi 

'eve! 


h ii;j 

, ii/ 

8 th |II / 

i 

tvel 


E 

l'J! 

U <i 

k> l/li 

cx. l 

Uo I 

Uto M 

!r> !r 

9 th level 



i 

i 1 ' 

10 th /eve/ 


ORE SHOOTS. 

The stopes on the “C” vein 
were very large and extended 
from near the surface to level 4, 
and in places somewhat below 
it. Three hundred feet below the 
surface the maximum horizontal 
length of 600 feet was attained, 
and the shoot practically con¬ 
nected with the south body of 
the Findley mine. Smaller stopes 
down to level 10 were opened on 
the Winze vein, which is as¬ 
sumed to be the “C” vein after having crossed over to the west side of the dike. 
On the lower levels the most important ore body occurred on the ‘‘D” vein, lying 


Scale 


0 
i_ 


200 

i 


400 feet 


j 


Fig. 50. —Cross section of Hull City mine, looking northwest (after 

F. G. Willis). 





























MINES BETWEEN ALTMAN AND GOLDFIELD. 


415 


just east of the dike. These stopes began near the Findley boundary line on level 4, 
where the “D” vein begins to split off from the main vein, and continued widen¬ 
ing down to level 10, where they are 500 feet long. The shoot continues, though 
the best values were found between levels 8 and 9. 

A third shoot follows the projection of the Glorieta shaft down to Hull City 
level 8. It connects on the south side all along with the ore body in the Vindicator 
No. 2 on the Wallace vein, and will be mentioned in more detail when that mine is 
described. 

VINDICATOR MINE. 

PRODUCTION AND DEVELOPMENT. 

The Vindicator Consolidated Gold Mining Company owns an irregular area 
of 30 acres on the southern slope of Bull Cliff, above the town of Independence. 
The property extends from the Hull City line on the northwest to the Lillie, Christ¬ 
mas, and Golden Cycle boundaries on the southeast, a distance of 1,400 feet. Most 
of the ore shoots lie on the Wallace and Trotter claims, which have a general north- 
northwest direction. The mine was opened in 1895 and has been actively worked 
since then. The total production up to January 1, 1895, is about $4,600,000, 
from which dividends to the amount of $1,225,000 have been paid. The output 
for 1903 and 1904 has been as follows: 


Output of Vindicator mine. 




1C03. 

1904. 



Amount. 

Assay 

value. 

Amount. 

Assay 

value. 

Smeltinc' orp _ ..... 

Tons. 

7,700 

S418,230 
74,929 

Tons. 

8,980 

8521,560 

Milling ore.. 

- 

4,728 

6,364 

103,121 





12,428 

493,160 

15,344 

624,687 


The main or No. 1 shaft is located close to the Lillie boundary line in the 
western part of the property. The elevation of the collar is 10,209 feet and sixteen 
levels are turned, the lowest (1,200-foot) level having an elevation of 9,009 feet. 
The relations of the levels are shown in fig. 52. Those most important for the pur¬ 
poses of this description are levels 8, 10, 12, 13, 14, and 16, corresponding to depths 
of 502, 650, 804, 904, 1,003, and 1,201 feet. Level 16 connects with level 12 of 
the Lillie. 

No. 2 shaft lies close to the Hull City line, 800 feet west-northwest of the main 
shaft. Its collar is 23 feet lower than that of the main shaft, and only seven levels 
are turned. Of these, level 6 is 500 and level 7 about 600 feet below the surface. 
Drifts on all levels from the main shaft explore pretty thoroughly the space between 
the Hull City and Lillie mines, while long crosscuts on levels 8, 12, and 14 open the 
south end of the property. The total length of shafts, drifts, and crosscuts on all 
levels is stated to be 12 miles, to which a considerable amount is added each year. 















416 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


WATER LEVEL AND OXIDATION. 

The Vindicator mine forms part of a drainage basin, in which are included 
the Findlejr, Hull City, Lillie, and Golden Cycle. First water was found on the 
500-foot level, where at one time 100 gallons a minute were pumped. At 1,200 
feet below the collar it was necessary to pump 500 gallons a minute. At the pres¬ 
ent time (1904) no pumping is done and the water stands a little below the 900-foot 
level. The shaft between the 800 and 1,200 foot levels was entirely dry, even dusty, 
and so were the drifts until the veins were crosscut, when a big stream issued. 
The water is potable, and for some time the supply for the town of Victor was 
drawn from the Vindicator pumps. All the veins are oxidized down to the 500- 
foot level, and part of the rock is reddish brown and soft. Even on the 800-foot 
level some of the veins are still oxidized. 

GEOLOGICAL FEATURES. 

As may be seen on the geological map, the Vindicator mine lies in the north¬ 
eastern part of a rounded area of syenite surrounded by breccia, and this syenite 
in its northern part connects by gradual transition with a branch of the Altman 
area of latite-plionolite. Short crosscuts to the northeast on the 500-, 650-, and 725- 
foot levels show that the breccia lies almost in the foot wall of No. 1 vein near 
the Vindicator and Lillie shafts, as it does near the surface. At the Sigel vein, in 
the extreme southeast part of the property, the rock is a very much brecciated 
latite-phonolite. A main contact between the massive rock and the normal breccia 
lies very close to No. 2 shaft and the Hull City line. A rock from level 6 of No. 2, 
30 feet west of the shaft, proved to be a breccia, as is all of the country rock in the 
adjacent part of the Hull City property. Examination of rock sections has shown 
that some of the supposed massive latite-phonolite from level 12, a few hundred 
feet south of the shaft, is really much brecciated. The same applies to some speci¬ 
mens from level 16, northwest of the shaft. In fact, the normal breccia in this 
part of the district is very apt to contain a large amount of latite-phonolite, and 
it is often impossible to draw a well-defined line between solid rock and breccia. 

The principal rock appearing in the workings from one end of the mine to the 
other is a latite-phonolite of normal type, with large porphyritic feldspar crystals, 
while syenite occupies relatively small areas. To distinguish between these closely 
allied rocks is often difficult, and in many places they are connected by transitions. 
Still it is somewhat surprising, in view of the prevalence of the syenitic rock on the 
surface, to find such small bodies of it in depth. The best known mass of syenite 
is exposed on several levels at and just west of the shaft. On the eighth (500-foot) 
level there is a sharp contact between latite-phonolite and syenite 50 feet south¬ 
west of the shaft. The latter rock continues for 100 feet southwest and then 
appears to gradually change to latite-phonolite. On level 10 syenite, with transi¬ 
tions to fine-grained types, appears between the shaft and the Vindicator vein, 30 
feet southwest, but the crosscut does not extend farther in that direction. On 
level 12a very fine-grained latite-phonolite appears at the station, but changes with 
sharp contact to syenite, which continues for 300 feet southward and there again 
borders sharply on latite-phonolite. On level 14 a similar contact is well exposed 


U. S. GEOLOGICAL SURVEY 


PROFESSIONAL PAPER NO. 54 PL. XXVI 




aa 

L 

TT 



B. STRATTON’S INDEPENDENCE AND STRONG MINES. 
































MINES BETWEEN ALTMAN AND GOLDFIELD. 


417 


and trends almost due north. The syenite is here 100 feet wide, as shown by the 
south crosscut. At the La Bella vein on level 8 a little syenite is exposed, and 
likewise on levels 8 and 12 along the western boundary line of the property, in both 
cases with fairly sharp contacts, but neither of these bodies appears to connect with 
that at the shaft. It would thus seem as if the latite-phonolite contained several 
intrusive masses of syenite which have a very irregular shape. 

There are very few phonolite dikes. One was noted on level 8 along No. 3 
vein, 350 feet northwest of the main shaft. Two basic dikes have been opened by 
the workings, both trending north-northwest and dipping very steeply west-south- 
west. One of these, which is more closely defined as a monchiquite, is reached by 
a crosscut northeast from the shaft on level 10 and* lies in unproductive territory. 
The other lies about 200 feet west of No. 2 shaft, and is exposed on levels 11, 12, 
and 13, as well as on level 7 of No. 2 shaft. In the latter place it flattens some¬ 
what and changes its strike. 

VEIN SYSTEMS. 

The trend of the main fissure near the surface is S. 60° E. from shaft No. 2 to 
the main shaft and to the Lillie shaft, a short distance east of which it seems to die 
out. The workings disclose, however, the same tendency as in the Hull City mine 
to throw out branches on both sides of the main fissure. The detailed structure in 
the Vindicator is very complicated, and there is considerable uncertainty as to the 
correct connection of the veins between the various levels, an uncertainty which 
can often be settled only by actual stoping operations. The difficulty is increased 
by the very tight character of the veins and the general absence of well-defined 
walls. 

At No. 2 shaft the principal vein is called the Wallace. Below level 5 this 
vein soon separates from that trending toward the Lillie shaft. It assumes a direc¬ 
tion of N. 30° W. and a dip of 80°, and has been followed for 400 feet south-south¬ 
east of the shaft down to level 13. In the southward widening angle between the 
Wallace and the Main or No. 1 vein lie several other veins of less importance, as 
shown on fig. 55. No. 1 vein is practically continuous to the Lillie shaft by the 
main shaft and gradually straightens up, so that at the Vindicator shaft it is almost 
vertical. 

No. 2 vein branches from No. 1 a little east of the Lillie shaft, and at the Vin¬ 
dicator shaft on level 8 lies 100 feet southwest of No. 1. A small and rich branch, 
the Vindicator, here lies between No. 1 and No. 2. It then seems to cross No. 1 
vein, 200 feet northwest of the main shaft, and continues diverging with a strike of 
N. 30° W. up to the boundary line of the property. It is possible, however, that 
there is no real crossing, but that No. 2 vein north of the shaft is simply a diverg¬ 
ing branch like the Lillie No. 2 vein on the south side of the same shaft. No. 3 
vein branches from No. 2 and lies a short distance east of it. These two veins, 
also known as the Campbell and Wood veins, are not definitely known above level 8. 
On level 16 No. 1 vein can not be definitely recognized, and the whole vein system 
seems to be materially different. 

In the southern part of the property lie the La Bella vein, known from the 
Christmas and Golden Cycle mines, and the Sigel and New veins, also opened in 


418 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

the latter mine. These southern and less important systems are opened by long 
crosscuts on levels 8, 12, and 14. Their trend is northwest or north-northwest and 
their dip very steeply southwest. They have proved productive for only a distance 
of 200 feet from the southern boundary of the Vindicator. 

The absence of cross veins is noteworthy. The two basic dikes in the northern 
part of the property carr} r no values and have no enriching influence. One of 
them, on the other hand, cuts off the ore shoot on No. 1 vein. 

The veins are generally sheeted zones of an average width of 3 to 6 feet, but 
in places swell to 20 feet. Well-defined walls are rarely seen. The country 
rock has an irregular roughly blocky structure, and the tight seams of which the 
veins usually consist seem scarcely better defined than the joints in the surround¬ 
ing latite-phonolite. On some veins a central seam with vugs is characteristic, but 
the cavities are very small. In the vicinity of the veins the latite-phonolite con¬ 
tains a little more disseminated dolomitic carbonates and pyrite than elsewhere, 
but even in the vein itself the percentage of these replacing minerals is small and 
does not greatly affect the appearance of the rock. Fluorite is sparingly present. 
As usual, the values are in the seams and, below the oxidized zone, consist of finely 
divided calaverite, often scarcely visible by the naked eye, loosely coating the thin 
quartz seams of the joints. Few other metallic minerals occur. Blende and galena 
are found in places, especially in the Sigel vein; molybdenite is likewise pretty gen¬ 
erally distributed and was specially noted from the stopes on No. 3 vein. Tetra- 
hedrite occurred in an unnamed vein on the deepest (1,200-foot) level, 200 feet 
northwest of the shaft. 

The ore, which is sometimes shipped as taken out, but more frequently screened 
and hand picked, is of high grade and for the years 1901 and 1902 averaged a little 
over $40 per ton. 

The smelting ore, which constitutes the larger part of an average daily output 
of 43 tons, contains about $58 per ton, while the milling ore, amounting to about 
two-thirds of the total ore production, averages $16 per ton. Very little silver is 
present. 

ORE SHOOTS. 

The most valuable ore body in the mine is that on No. 1 vein, which enters 
Vindicator ground from the Lillie between levels 5 and 11, and with a northwesterly 
pitch of 50° ceases somewhat below level 14. 

Another shoot continues from the Lillie No. 2 vein into Vindicator ground, 
but the richest part of it occurred on a spur from this vein called the Vindicator 
from levels 12 to 14. Excellent shoots have been found 400 to 500 feet north- 
northwest of the shaft and in the deepest levels, on No. 2 and No. 3 veins, which 
here lie on the northwest side of No. 1 vein. 

The Wallace vein or spurs close to it have carried a large stope practically from 
the surface down to level 13, the deepest from which it has yet heen opened. It 
connects with the Glorieta shoot of the Hull City mine and pitches steeply north¬ 
ward. Shoots of smaller size have been opened on the La Bella, Sigel, and New 


veins. 


MINES BETWEEN ALTMAN AND GOLDFIELD 


419 



Fig. 51.—Map of level 12, Vindicator mine, showing vein system; elevation, 9,405 feet. 










420 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 



Scale 

o 200 400 feet 

i-1-1_i_i 

Fig. 52.—Cross section of Vindicator mine along line L-J on plan, showing stoped 
portions of veins; looking northwest. 


DETAILS OF XOS. 1, 2, 
AND 3 VEINS. 

On level 8 No. 1 vein en¬ 
ters, strongly developed, 
from Lillie ground, with 
wide stopes, which con¬ 
tinue practically un¬ 
broken for 400 feet north 
of the shaft. No. 2 vein 
begins small, 50 feet 
southwest of the shaft, 
and continues with stopes 
for 300 feet, near the end 
of which it seems to con¬ 
nect with or cross No. 1 
vein. 

On level 10 No. 1 vein 
lies close to the shaft and 
continues northwest, 
with large stopes reach¬ 
ing down to the next 
level. Two hundred feet 
northwest of the shaft 
No. 2 vein intersects it. 
Stopes extend to a point 
500 feet from the shaft, 
where the vein is cut off 
by a basic dike. The 
Vindicator spur lies 35 
feet southwest of the 
shaft. No. 2 vein, on the 
northeast side of the 
main vein, is worked 
near the north end of the 
property, 500 feet north- 
northwest of the shaft. 
This shoot, which is not 
known higher up, con¬ 
tinues down to level 14 
with a steep north-north- 
west pitch. On level 10 
the stopes show 6 feet 
of solid latite-phonolite 
cut by a few tight seams, 













































( 


MINES BETWEEN ALTMAN AND GOLDFIELD. 421 

with a little fluorite. The ore, however, assays 6 ounces per ton and is shipped as 
taken out. 

On level 11 No. 1 vein is not seen at the station, but appears 80 feet to the 
northwest. It is stoped for 500 feet up to the basalt dike, where both shoot and 
vein seem to be cut off. The stopes on No. 2 continue from above, 500 feet north- 
northwest of the shaft. A new vein called No. 3 here appears, 35 feet to the north¬ 
west of No. 2, diverging slightly northward. Excellent stopes have been opened 
on No. 3 at the northern boundary line, the shoot pitching steeply northward. 
No. 3 shows first 400 feet northwest of the shaft as an oxidized seam, 2 inches 
wide, often assaying 7 ounces per ton. The screenings of the drift run 31 ounces. 
It then widens and forms a shoot 180 feet long and up to 15 feet wide. The latlte- 
phonolite is fresh, but contains a little pyrite. No well-defined central seams are 
here visible, but there are irregular cracks, oxidized in places and trending in every 
direction, horizontal as well as vertical. 

On level 12 the shoot on No. 1 vein was very productive and extended from 
near the shaft up to the basaltic dike. Extremely rich ore was stoped from the 
Vindicator spur, beginning at a point 100 feet northwest of the shaft and continu¬ 
ing for 200 feet. From a dark-brown oxidized streak 1,500 pounds were here 
mined which contained $15,000. The stopes on No. 2 vein are small, but those 
on No. 3 are very extensive, reaching to the northern boundary line of the prop¬ 
erty, where the values are cut off by the same basic dike which affects the shoot 
on No. 1 vein. 

On level 13 the workings on No. 1 continue as before to the basic dike. The 
Vindicator spur is small. No. 2 vein carries a large stope up to the basic dike, but 
No. 3 vein is not known and, it is believed, joins No. 2 above the level. 

On level 14 the No. 1 shoot was 400 feet long and very rich. Some of the 
stopes are 28 feet wide. As on the upper levels, it is cut off by the dike at a point 
650 feet northwest of the shaft. The shoot descends below this level, but does not 
reach level 16, the deepest in the mine. Stopes on No. 2 vein, 500 feet north- 
northwest of the shaft, also descend to level 14. The vein has not been crosscut 
as yet on level 16. 

Some work was being done in 1904 by lessees on level 7 of Vindicator No. 2 
shaft, which is 12 feet above level 10 of No. 1 shaft and 625 feet below the surface. 
The veins worked here, 250 feet east of the shaft, correspond to No. 2 and No. 3 
veins, and are also known as the Wood and Campbell veins. These veins intersect 
the basic dike, and the values are said to stop against it on its west side, as they 
do on the east side in the lower levels. 

DETAILS OF WALLACE VEIN. 

The Wallace vein, together with several spurs near the surface, has been 
stoped for a horizontal distance of 200 or 300 feet from near the collar of shaft 
No. 2 down to level 13, the shoot pitching slightly northward. The vein appar¬ 
ently forms the extension of the Sigel vein in the'southern part of the property, 
but probably does not actually continue across. Branching off to the east from 
Wallace vein are several seams of less importance. On one, called No. 4, some 


422 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


good ore has been found on level 12. Another, the “ Jumbo,” is very large and 
contains much quartz as filling and replacement, but no values are encountered 
(fig. 51, p. 419). 

DETAILS OF SOUTHERN VEINS. 

The Christmas or La Bella vein can not be followed far northward from the 
boundary of the Christmas mine. It has been stoped in the Vindicator practically 
from the surface down to a depth of 500 feet from No. 6 shaft, though the stopes 
are not more than 100 feet long; they connect with Christmas workings. The vein 
has also been opened and stoped on levels 8 and 12. On level 8 the stopes are 50 
feet long and 6 feet wide. On level 12, 750 feet below the surface, the rock is very 
hard and tight and the small stopes are located close to the Christmas line. 

The Sigel and New veins have no surface workings, but are opened by a cross¬ 
cut from No. 6 shaft on level 5, 350 feet below the surface, and continue into Golden 
Cycle ground. The strike is here N. 60° W. On level 8, in the main shaft, the 
veins are narrow, but with well-defined walls. The central seam of the New vein, 
which lies 80 feet southwest of the Sigel, contains 3 ounces per ton in places. On 
level 12 there are important shoots, the Sigel being stoped for 130 feet from tne 
Golden Cycle line and 160 feet high, while the New vein, which here branches from 
the Sigel near the boundary line, is stoped for a distance of 100 feet. The veins 
are here partly oxidized and show a narrow central seam with several tight par¬ 
allel cracks. Galena and zinc blende, with quartz and calaverite, coat the seams. 
The stopes are 4 or 5 feet in width. The screenings which constitute ore contain 
about 3 ounces per ton. 

On level 14, 950 feet below the surface, both veins are again opened and the 
New vein stoped 5 feet wide. It consists of a narrow, partly oxidized seam with 
tellurides and coated with dolomite. 

CHRISTMAS MINE. 

Between the Vindicator and the Golden Cycle mines lies the privately owned 
Christmas claim. Although a small property, with the only vein thus far produc¬ 
tive confined to the southwest corner, the mine has a reported production of 
$330,000. It is opened by a main shaft with eight levels, the lowest 605 feet 
below the collar, which has an elevation of 10,159 feet. Fig. 53 shows the posi¬ 
tion of the veins near the shaft, according to surveys of V. G. Hills. The drifting 
is confined chiefly to the southwest corner of the claim, though there is a crosscut 
250 feet long northeast to the Lillie line and a longer crosscut due east to the same 
line on the 514-foot level. The mine is now worked on a small scale by lessees. 

On the surface a narrow northeasterly trending belt of breccia separates an 
area of latite-phonolite on the southeast from the Vindicator area of syenite on 
the northwest. As shown underground the breccia contains a large amount of 
latite-phonolite, and the contacts separating it from this rock are very indistinct. 
The stations at the 239- and 515-foot levels are in breccia. In the upper level 
breccia continues northeast through the 250-foot crosscut and is cut by a narrow 


MINES BETWEEN ALTMAN AND GOLDFIELD. 


423 


£/. 10.158' 


Z.-ZM 22,9'level 


dike of latite-phonolite 150 feet from the shaft. At the end of this crosscut is 
another dike, said to be syenite. The main vein west of the shaft is in latite- 
phonolite. On the 515-foot level brecciated latite-phonolite appears at the station, 
but changes to massive rock of the same kind 75 feet northeast, at the first vein. 
Four hundred feet east of the shaft in the long drift and crosscut the latite-phonolite 
changes to denser phonolitic rock, 
and a dike of syenite is met at 
the Lillie line, possibly the same 
as that in the crosscut on the 
239-foot level. On the west side 
from the main shaft breccia con¬ 
tinues to the La Bella vein. 

The principal vein is the La 
Bella, which is also worked on both 
adjacent properties. Its strike is 
N. 45° W. near the surface, but it 
swings to N. 34° W. on the lowest 
level. The dip is nearly vertical in 
the upper levels, but turns 70° SW. 
in the four lower levels. Two or 
three lesser veins diverge toward the 
southeast; one of them, the Talbot, 
crops near the small Wilkinson shaft 
and is cut on several lower levels 
dipping very steeply northeast ; a 
second vein is opened at No. 3 shaft, 

400 feet east-southeast of the main 
shaft, and is also cut on the 514- 
foot level. 

The La Bella vein consists of 
several closely contiguous branches 
converging toward the northwest. 

In the vein the rock is often re¬ 
markably fresh, locally with well- 
preserved augites; in one place a 
transition to syenite was noted. 

There are usually several narrow and 
tight seams and many minor cracks, 
all coated with carbonates, quartz, 
and tellurides. 

Two shoots have been mined. One, beginning just north of the shaft and 
up to 10 feet wide on the 239-foot level, continues to the 605-foot level and thence 
pitches northward into Vindicator ground, 200 feet northwest of the shaft, where 
it has been mined on level 12, about 150 feet below the deepest Christmas level. 
A second shoot lies near the Golden Cycle line, which is only 50 feet southeast of 



Fig. 53.—Cross section through Christmas shaft, showing Christmas 
veins; looking northwest. (After V. G. Hills.) 

































424 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


the shaft, and from the lowest levels pitches into that property; on the 514-foot 
level at the boundary line it is up to 15 or even 20 feet wide. The same shoot 
has been opened in the Golden Cycle on level 9, 400 feet below the 605-foot Christ¬ 
mas level. 


LILLIE MINE. 

The Lillie claim adjoins the Vindicator property on the southeast and occupies 
an area of 7 acres. It was operated by the Lillie Gold Mining Company (Limited), 
of London, but is now the property of the Vindicator Company. The total pro¬ 
duction approaches $1,300,000, and the dividends paid amount to about $400,000. 
The development consists, besides several small shafts, of a principal shaft 1,526 
feet deep, with twelve levels turned, as shown in fig. 54. The elevation of the 
collar is 10,222 feet; level 12 connects with the deepest (1,200-foot) Vindicator 
level 16 at an elevation of 9,009 feet; the shaft was sunk 300 feet deeper. The 
workings, while occupying only a small horizontal space, are extensive, and the 
old stopes on practically every level above 12 connect with the Vindicator drifts, 
the line being but 175 feet distant from the shaft. To the southeast the drifts 
extend only 200 feet; but on level 8 an exploratory drift reaches 600 feet from 
the shaft in this direction. The mine has not been operated for several years. 
The water is held at the same level as in the Vindicator. There was little oppor¬ 
tunity for examination of geological features, which, however, are similar to those 
in the Vindicator. The prevailing rock is latite-phonolite, while breccia is apt to 
appear on the northeast side of No. 1 vein. 

The Lillie has two main veins, named No. 1 and No. 2. No. 1 is the principal 
one and really forms the south end of the persistent lode which traverses the 
Findley, Hull City, Vindicator No. 2, and Vindicator shafts, holding a direction of 
N. 60° W., and at intervals sending out branch veins which diverge toward the 
north. The Lillie No. 1 is very nearly vertical, as shown in fig. 54. No. 2 vein 
branches from it 50 feet south of the shaft and lies on the southwest side; at the 
Vindicator line it is about 100 feet from No. 1. 

The main vein had one very large ore shoot, which at the surface was 200 feet 
long and at a depth of 550 feet pitched into Vindicator ground, and here continued 
to a depth of 900 feet, at the same time lengthening its horizontal dimension. 
Some of the Lillie stopes were up to 20 feet wide. On the branch (No. 2) vein 
very rich ore occurred at the intersection with No. 1. Beginning 200 feet below 
the surface, the shoot on No. 2 continued with a length of 200 to 300 feet to a 
depth of 800 feet and then entered the Vindicator property, in which, however, it 
did not persist very far. The developments below the 800-foot level are said to 
have shown very little ore in the Lillie. 

GOLDEN CYCLE AND THERESA MINES. 

PRODUCTION AND DEVELOPMENT- 

The Golden Cycle Mining Company owns a roughly rectangular area of 25 
acres adjoining the Vindicator and the Christmas on the southeast side. It is one 
of the large mines of the district, notable for its output of medium-grade ore. The 


Lillie side tine 


MINES BETWEEN ALTMAN AND GOLDFIELD 


425 


Lillie main shaft 
collar 10222 



No. 2 shaft 



Scale 

200 400 feet 

i_i-1 


Fig. 54.—Cross sections of the Lillie vein, perpendicular to the plane of shafts 1, 2, and 3, showing stopes on veins. 













































426 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


production, which dates from 1896, amounts to nearly $4,000,000 up to January 1, 
1905. Dividends of $350,000 have been paid in the same time. 


Production of the Golden Cycle mine from 1902 to 1904., inclusive. 


Period. 

Amount. 

Gross 

Value. 

July 1, 1902-Dec. 31, 1902. 

Tons. 
18,751 
35,300 
22,479 

S408.220 

831,900 
400,194 

Jan. 1, 1903-Dec. 31, 1903 ... 

Jan. 1, 1904-Dec. 31, 1904 a .. 



a Mine was closed during May, June, July, and August, 1904. 


The main shaft is located on a bluff just north of the town of Goldfield, and 
the elevation of its collar is 10,066 feet, or 143 feet below the main shaft of the 
Vindicator. The shaft is 1,030 feet deep; level 3 is 276 feet below the collar, 
while the subsequent ones are respectively 400, 500, 600, 700, and 1,000 feet below 
the same datum. There are also two smaller shafts—the Anna, on the Harrison 
vein, and the La Bella, on the Revenue system. A tunnel with an elevation of * 
9,897 feet gives access to the upper workings. The total developments amount to 
several miles. 

The Theresa property consists of the claim of the same name, adjoining the 
Golden Cycle on the east, and was until recently worked in conjunction with the 
Golden Cycle. It is developed by a shaft situated 200 feet southeast of the main 
shaft of the Golden Cycle. The bottom level is the same as level 7 of the Golden 
Cycle, but the workings of level 8 of the latter mine have also been extended into 
Theresa ground. Four hundred feet north of the Theresa shaft is the Tateman 
shaft, which explores the upper part of the Revenue system down to an elevation 
of 9,927 feet. There is also a crosscut 700 feet long on level 5 of the Theresa shaft 
which opens the whole northern part of the claim up to the boundary underneath 
the Tateman shaft. The drifts and crosscuts on the Theresa amount to several 
thousand feet. 

The Gold Knob shaft was sunk 600 feet deep in the breccia 850 feet southwest 
of the Golden Cycle shaft and in the line of extension of the Legal Tender vein. 
The crosscuts are said to have thus far failed to develop any veins. 

The Golden Cycle connects with the Vindicator drainage basin. In June, 
1903, level 10 was kept dry by pumping 50 gallons a minute, most of which came 
from the Legal Tender system, while the Revenue veins are almost dry. The 
Vindicator was then pumping 210 gallons a minute. Later on, in March, 1904, 
pumping was discontinued in both mines and water rose to between levels 8 and 9. 
At the end of 1904 the Golden Cycle, the only mine then pumping, kept the water 
below level 10 by raising 300 gallons a minute. 

The mine is free from gas except a small amount occasionally occurring in the 
long crosscut southwest on level 9. 

GEOLOGICAL FEATURES. 

On the surface the shaft is situated in an oblong area of latite-phonolite, 
separated by a strip of breccia 200 feet wide from the Vindicator area of syenite, 














MINES BETWEEN ALTMAN AND GOLDFIELD. 


427 


which reaches to the southeast about as far as the Christmas mine. The under¬ 
ground developments do not correspond to the surface relations, hut indicate that 
the southern half, at least, of the area of latite-phonolite forms a flat body under¬ 
lain by breccia and that in depth it in all probability connects with the Vindicator 
rock mass. On the tunnel level the rock south and west from the shaft is a breccia, 
while latite-phonolite extends from the Legal Tender vein close to the shaft up to 
the Christmas line. On level 3 latite-phonolite begins 30 feet north of the shaft 
and on levels 4 and 5,130 feet from the same place. The rock is brecciated in places 
along the La Bella vein. On level 6 the same contact is found 350 feet north of 
the shaft in the crosscut which leads direct to the Revenue veins. Brecciated 
rock is again met in spots in the La Bella and Sigel veins. Finally, on level 8 the 
contact lies 400 feet north of the shaft at the Middle vein, and the Legal Tender 
vein is in breccia all along for 270 feet northwest of the shaft. Latite-phonolite 
extends from the Middle vein up to La Bella, and here, as in other levels, doubtless 
connects with the Vindicator area. No normal syenite was seen in the mine. The 
workings on level 10 were not far advanced at the time of the first visit, in June, 
1903, and showed only breccia. A crosscut on level 9, 600 feet long, explores the 
southwestern territory and shows only normal breccia. For the last 100 feet the 
breccia is fine-grained and crumbling, almost without secondary alteration; it con¬ 
tains much phonolite. 

No basic dikes have been found. On level 9 the Harrison vein is in places 
followed by a narrow phonolite dike. Another dike, which also seems locally 
irregular and nonpersistent, in places lies closely to the northeast of Legal Tender 
vein. It was seen on level 3, where it is 35 feet wide and 40 feet from the vein, on 
level 5, and on level 8, where the northwest end of the Legal Tender vein, 270 
feet northwest of the shaft, is in phonolite. It is probably the same dike which 
lies parallel to the Theresa East vein, a spur of the Legal Tender, on levels 7 and 8, 
near the Theresa line. 

THE VEINS IN GENERAL. 

The Golden Cycle mine depends for its ore on three vein systems with a general 
northwesterly, slightly diverging strike and very steep southwesterly dip. If 
continuous these systems would intersect at a point near the Gold Knob shaft in 
Goldfield. The Harrison vein strikes west-northwest and is opened for a distance of 
500 feet about 100 feet southwest of the shaft, and has also been cut in a shaft on 
the Aluminium claim a few hundred feet farther north-northwest. Four hundred 
feet west of the shaft it has, on upper levels, an important spur called the Anna. 

The Legal Tender vein strikes nearly due northwest, and on level 9 lies immedi¬ 
ately north of the shaft; its dip is very steep to the southwest. It has been opened 
for a distance of about 700 feet, beginning in Theresa ground and extending to a 
point 300 or 400 feet northwest of the shaft; drifts are extended on it on all levels, 
including 10. A spur near the shaft and another called the Theresa East vein 
have proved valuable. 

The Revenue system is the most complicated. It lies 500 to 800 feet north of 
the shaft, and the various veins trend north-northwest. Between the Revenue 
and the Legal Tender on levels 6 and 8, but not above, lies the Carr or Middle vein. 


428 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

In the Revenue the most southerly is the Revenue vein, known on all upper levels 
down to 7, while it is less well developed on 8 and 9. It has several spurs. The 
Sigel vein, opened on level 6 at the Vindicator boundary, lies in the continuation of 
the Revenue, but the actual connection has not been established. About 100 feet 
north of the Revenue is the La Bella vein, known on levels 3 to 9, inclusive. A vein 

carrying small values was 
cut near the end of the long 
southwest crosscut on level 
9; it occured in the loose, 
unaltered breccia which 
there forms the country 
rock. 

OXIDATION. 

Oxidation has pene¬ 
trated to the bottom level 
along most of the seams, 
and the ores invariably 
pan free gold. Calaverite 
is, however, found occa¬ 
sionally, and one vein, the 
Middle, on level 8, is not 
oxidized, possibly because 
not reaching: to the surface. 
The natural water level is 
not positively known, but 
is believed to have had a 
depth of about S00 feet. 

VEIN STRUCTURE AND ORE. 

The veins as a rule are 
narrow sheeted zones, in 
many cases with a pro¬ 
nounced central seam and 
not quite so tight as in the 
Vindicator, though the 
rock is often very fresh 
within the veins. The 

seams are coated by 

quartz, dolomitic carbon¬ 
ates, and a little fluorite; celestite needles also occur. Native gold is the principal 
ore mineral, with a little unchanged calaverite and occasionally a little pyrite, 
galena, and zinc blende. A spur vein along the phonolite dike at the Theresa East 
vein contains much galena and zinc blende, but carries low values in gold. The 
breccia and latite-phonolite throughout the productive ground contain a little 
pyrite and dolomite, but the alteration is never pronounced. The alteration is 

strongest within the veins and, as shown by the crosscut on level 9, is apt to disap- 







MINES BETWEEN ALTMAN AND GOLDFIELD. 


429 


pear entirely away from the strong vein systems. The ore is sometimes shipped 
as broken, but often it is found more advantageous to screen it; its grade is low 
compared with some other mines like the Vindicator, averaging between $20 and 
$25. On the other hand, the tonnage is considerable. 

ORE SHOOTS. 

The ore shoots of the Golden Cycle are not more than a few hundred feet long; 
they are either vertical or pitch steeply northward, as, indeed, seems to be the rule 
throughout this part of the district. No cross fissures are present and no structural 
conditions seem to influence the ore shoots, except possibly spurs and branches 
which sometimes have an enriching effect. On the Harrison vein, with the Anna 
spur, a good ore shoot, 10 feet wide in places, went to the surface and was also stoped 
on the tunnel level. On levels 3 and 4 it lengthened to 500 feet and the Anna 
spur proved very productive. Lower down it decreased in length to 300 feet on 
level 7. On levels 8 and 9 the vein is of low grade; it here appears as a narrow 
sheeted zone with a central clay seam from which values of $10 may be obtained. 

The most productive vein is the Legal Tender. Its shoot is said to have been 
poor and short on the highest levels, though it has been stoped on these in Theresa 
ground. The shoot has a decided northward pitch. On level 3 the shoot is 250 
feet long and lies on both sides of the shaft. On level 6 it increases its length to 
400 feet. On level 8 the shoot extends 300 feet northwest from the shaft and has 
been very rich, while the vein breaks up southeast of the pay shoot. Finally, on 
level 9 the shoot is 400 feet long and values are maintained. In the deepest level 
the Legal Tender vein shows 7 to 10 feet wide with entirely oxidized seams in fresh 
pyritic breccia. In stopes between levels 8 and 9 the payable portion is 6 feet 
wide, without well-defined walls. The rock is a fresh breccia cut by a central seam 
and many smaller ones, all brown and oxidized. The Theresa East vein first appears 
on level 7, 35 feet east of the Legal Tender, and much ore was stoped on it between 
levels 7 and 8. On level 8 it dips 60° SW. and joins the Legal Tender 30 feet above 
level 9. The ore extracted from a single raise from level 9 to 8 near the Theresa 
boundary line is said to have yielded $25,000. The vein is 5 feet wide, and shows 
oxidized seams. Screenings often yield 6 ounces per ton. The Middle vein shows 
a good ore shoot on level 8, with a very rich central seam, sometimes containing 
200 ounces per ton. 

An important ore shoot has been mined on the Revenue vein from the surface; 
it is 200 feet long on the tunnel level and 10 feet wide in places. These large stopes 
continue through succeeding levels from 3 to 8, inclusive, and show at least one im¬ 
portant spur vein. 

On the La Bella vein shorter stopes connecting with the Christmas mine were 
carried to the surface from the tunnel level, while on level 3 the vein was small and 
the ore body short. On levels 4 and 5 the shoot was much better and up to 150 
feet long. Ore continues on this vein down to level 9, the deepest yet opened. The 
vein here shows a small central seam carrying a little calaverite, but mostly oxidized. 
Little fluorite is present. The screenings from a width of 3 or 4 feet contain 
about 2 ounces per ton. 

13001 — No. 54—06 - 29 


CHAPTER VII—MINES OF BATTLE MOUNTAIN (EAST GROUP). 


GENERAL INTRODUCTION. 

Battle Mountain rises directly north of Victor, in the southern part of the 
volcanic area. On the northwest it is separated from Raven Hill by Arequa Gulch, 
and on the southwest from the granite mass of Squaw Mountain by a well-marked 
saddle. On the south Battle Mountain merges into the granitic slope upon which 
is built the town of Victor. On the southeast it is separated by Wilson Creek from 
Big Bull Mountain and on the north is connected by an open saddle with Bull Hill. 

5 The principal rock of Battle Mountain is a volcanic breccia of mingled phono- 
litic and granitic detritus. This breccia, which is bounded on the south In the 
nearly vertical rim of the Pikes Peak granite, is intricately intruded by masses of 
syenite and latite-phonolite and by phonolite and “basalt dikes. 

The mines of Battle Mountain are not only numerous, but constitute the most 
productive group in the entire district. Some of the ore bodies are entirely in 
breccia, others are entirely in granite, and still others are partly in breccia and partly 
in granite, or in some cases in phonolite or “ basalt dikes. On the northwest slope 
of the mountain are the Eclipse and Carbonate Queen mines. On the south slope, 
nearest Squaw Mountain, are the Ajax, Dead Pine, and Gold Coin mines, the latter 
in the town of Victor and not strictly on Battle Mountain. East of these mines is 
another line comprising the Granite, Monument, Dillon, and Mary C ashen mines. 
East of these again are the Portland, with workings extending under the summit and 
northern slope of the hill, the Strong, and Stratton’s Independence mines. 

PORTLAND MINE. 

INTRODUCTION. 

The Portland mine, the largest in the district, is on Battle Mountain, just 
north of Victor. The original Portland claim, located by James Doyle early in 
1892, was a small triangular fraction on the south slope of the mountain and about 
300 feet northwest of Stratton’s famous Independence claim. Doyle entered into 
partnership with James Burns, and soon afterwards John Harman was gN on a 
third interest. In a short time the three prospectors discovered ore, but were at 
once involved in litigation with surrounding claim owners. W. S. Stratton, how¬ 
ever, came to their aid, additional claims were acquired, and in 1894 the present 
company, capitalized at $3,000,000, was organized, with Stratton as its first presi¬ 
dent. The holdings of the company at that time included the Portland, Anna Lee, 
Bobtail, Hidden Treasure, Scranton, and Captain claims. Other purchases followed 
in succeeding years, until at present the Portland Gold Mining Company owns about 
430 


U. S. GEOLOGICAL SURVEY 


PROFESSIONAL PAPER NO. 54 PL. XXVII 





■mmm 


' 






i$t 


from the south 


THE PORTLAND 







































) 


MINES OF BATTLE MOUNTAIN, EAST GROUP. 431 

183 acres in the shape of an irregular strip of territory, nearly a mile long and about 
one-third of a mile wide, which stretches north and south over the eastern summit 
of Battle Mountain. South of the Portland property are those of the Stratton’s 
Independence (Limited), and the Strong Gold Mining Company; west of it are the 
Dillon, Monument, Granite, and Ajax mines; on the north the Blue Bird and Last 
Dollar mines; and on the east the Modoc and Rigi mines. 

At present the mine has three working shafts and the largest and most com¬ 
plete equipment in the district. The Portland Company operates its own mill near 
Colorado Springs. 

PRODUCTION AND DIVIDENDS. 

The following table, compiled from the admirable annual reports of the Port¬ 
land Company, gives the tonnage, gross value, and average value per ton of the ore 
raised from the mine, also the dividends from April 1, 1894, to the end of the year 
1905. In the next to the last column is given the proportion of silver to gold in the 
ore for those years for which data are obtainable. This proportion is expressed fyy 
giving the ounces of silver present with 100 ounces of gold. 

Production and dividends of the Portland mine. 


1894 

1895 
1896. 

1897 

1898 
1899. 

1900 

1901 

1902 

1903 

1904. 

1905. 


Total 


Year. 


Net tons. 

Gross value. 

Average 
value 
per ton. 

Ounces of 
silver per 
100 ounces 
of gold. 

Dividends. 

7,826.286 

$553,975. 75 

840. 78 


*67,290 

.31,616. 346 

1,700,094.89 

53,94 


479,790 

23,598.172 

1,116,128. 29 

47.29 


360,000 

18,852. 224 

1,177,642.65 

62.46 


360,0C9 

27,798. 850 

1,879,681.96 

67.61 


570,000 

38,548. 090 

1,951,219. 34 

50. 61 

6.87 

720,000 

60,786. 755 

2,351,369.26 

38.68 

4.30 

750,000 

76,905.550 

2,408, 413. 23 

31.31 

2. 41 

720,000 

89,664. 279 

2,334,023. 76 

26.03 

(°) 

270,000 

90,244. 582 

2,608,993.59 

28.91 

(o) 

360,000 

96,521. 385 

2,597,993.82 

26.91 

(“) 

720,000 

109,232.000 

2,422,033. 42 

6 23.60 

(“) 


671,394,519 

23,101,569.96 



5,377, 80 


a Output for this year given as ounces of gold. 

t> Low-grade ore from dumps (8,246 tons at $5.84 per ton) is not included in this average. 


UNDERGROUND DEVELOPMENT. 

According to the report of Mr. F. M. Kurie, manager, the linear development 
of the Portland mine, including drifts, crosscuts, shafts, winzes, and raises amounted 
on January 1, 1905, to 30 miles 3,513 feet.® From 3 to 4 miles of new development 
are completed each year. 

The main working shaft is the No. 1, or Burns, 1,120 feet deep, situated on the 
south slope of Battle Mountain near the south end of the Portland property. The 
No. 2 shaft, 1,282 feet deep, lies 750 feet about north-northeast from the Burns 
shaft, and 162 feet higher up on Battle Mountain. The No. 3 shaft, 1,155 feet 


a Total development to January 1, 1906, 34 miles 3,466 feet. 











































432 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT, 



Fig. 56.—Plan of the Portland mine, showing the boundaries of the property and parts of some of the principal levels 
















433 




MINES OF BATTLE MOUNTAIN, EAST GROUP. 

deep, lies 1,900 feet a little west of north from the Burns shaft and 1,300 feet nearly 
north-northwest from the No. 2 shaft; it is on the north slope of Battle Mountain, 
just below the summit, and its collar is 250 feet above that of the Burns shaft. An 
adit over 3,100 feet in length enters Battle Mountain near the collar of the Burns 
shaft and connects with the No. 2 and No. 3 shafts at about 162 and 250 feet below 
the surface, respectively. Through this adit timbers are taken in to these shafts 
and ore run out to the ore house near the Burns shaft. 

Besides the shafts mentioned are a number of old openings, such as the Anna 
Lee, Bobtail, Diamond, Scranton, and Wisconsin shafts, formerly worked as inde¬ 
pendent mines, but at present serving only for ventilation, and two small shafts, 
the Colorado City and Hawkeye, near the north end of the property, which have 
recently been connected with the main Portland workings. Since the time of visit 
the Lowell shaft, northwest of the Burns shaft, has been sunk to a depth of 170 
feet, and stopes have been opened on three levels. 



The principal levels now worked are designated as follows, the figures referring 
to the collar of the Burns shaft: The adit level, the 220-foot level, the 350-foot level, 
the 500-foot level, and thence levels at intervals of approximately 100 feet down 
to the 1,100-foot level. An idea of the general plan and extent of these levels 
may be had from figs. 56 and 57. 

GEOLOGICAL FEATURES. 

The workings of the Portland mine are partly in the breccia and eruptive rocks 
of the Cripple Creek volcanic neck and partly in the encircling granite through 
which these volcanic materials were ejected and intruded. (See PI. V, p. 26.) 
The granite is of the Pikes Peak type, 0 such as underlies the town of V'ctor and is 
exposed on Squaw Mountain. It is petrographically described on pages 43 to 45 

a Mathews, E. B., The granites of Pikes Peak, Colorado: Bull. Geol. Soe. America, vol. 6, 1894, p. 472. See also 
Geology and mining industries of the Cripple Creek district, Colorado: Sixteenth Ann. Rept. U. S. Geol. Survey, pt. 2, 
1895, pp. 22-23. 



























434 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


of this report. It is normally rather coarse grained, with conspicuous porphyritic 
crystals of pink microcline. A tendency toward gneissic structure is frequently 
noticeable. 

The common breccia of the Portland mine is a hard, rather even-textured 
gray rock in which the breccia structure is seldom very conspicuous. Recognizable 
fragments of phonolite or andesite over an inch in diameter are rare, and the breccia 
in which occur the ore bodies of the Captain and Hidden Treasure veins, near the 
No. 2 shaft, is so fine grained and homogeneous that its true character might easily 
escape detection by an eye untrained to its peculiarities or familiar onl} 7 with the 
more obvious nature of the breccia prevailing in the Raven Hill mines. Locally, 
however, blocks of granite, some of them as much as a foot or even 6 feet in diameter, 
occur within the breccia, particularly in the vicinity of the contact with the granite 
wall which limits the breccia on the south. This granitic breccia is very well shown 
on the 500-foot level, in the west crosscut to the Bobtail vein, northwest of the 
Burns shaft. Although such large fragments of granite are not common in the 
breccia of the northern part of the mine, yet close inspection of the finer grained 
phases, such as constitutes the country rock of the Captain veins, usually reveals 
little bits of pink microcline derived from the comminution of the granite. The 
microscope shows that together with particles of microcline and quartz of granitic 
derivation occur splinters of plagioclase and small fragments of the feldspathic ground- 
mass of andesitic and phonolitic rocks. No ferromagnesian minerals have been 
seen in any of the volcanic breccia of the Portland mine. Secondary pyrite is 
almost everywhere present, disseminated in varying abundance through the rock 
and usually accompanied by more or less calcite. 

In certain parts of the mine the breccia exhibits banding, which in some cases 
closely resembles ordinary bedding. Such a structure was noted on the 600-foot level 
east of the No. 2 vein, in a tine-grained phase of the breccia resembling a tuffaceous 
sandstone. The bands here are rather indistinct and are due to not very sharply 
differentiated alteration of slightly coarser layers with the prevailing fine grained 
material. Similar banding occurs in the northern part of the mine on the 500-foot 
level in the country rock of some of the Captain veins. The bands here are gener¬ 
ally nearly horizontal. They are not persistent, but fade out gradually into the 
fine-grained homogeneous breccia. The structure is best exhibited, however, south 
of the Burns shaft on the 220-foot level. Here also the banding occurs in an unus¬ 
ually fine-grained tuffaceous phase of the breccia which grades both horizontally 
and vertically into coarser material showing no banding. The bands are a foot or 
two thick and are nearly horizontal. The rock cleaves parallel to the bands and 
thus heightens the effect of regular stratification. The banded structure, however, 
is very local and passes by insensible gradations into coarser breccia, in which no 
bonding is perceptible. 

The origin of this handing in the tuff breccia is not clear. There is no evidence 
of the former existence of any considerable water body in which stratification might 
have taken place, nor do the constituent particles of the breccia appear waterworn 
when examined in thin section. It is probable that the structure is a very local 
phenomenon, incidental to the accumulation of the volcanic ejectamenta, and that 
it is to be ascribed to the winnowing action of air currents on fragments thrown up 



JULIUS BIEN & CO N Y 





















































435 


MINES OF BATTLE MOUNTAIN, EAST GROUT. 

from the old crater, to the sorting of particles by rolling down slopes, or to slight 
difference in size of the comminuted fragments thrown out by successive volcanic 
explosions. 

The contact between the granite and breccia is an irregular surface which 
plunges steeply down under the breccia to the north and east. Its dip is rarely less 
than 70°, is frequently approximately vertical, and in places forms what would be 
an overhanging cliff were the breccia removed. Some idea of the irregularity and 
general steepness of this contact may be had from PI. V (p. 26). As is there well 
shown, the granite in the Portland workings forms a bold promontory jutting into 
the breccia-filled funnel of the Cripple Creek volcano. Along the northern scarp of 
this promontory, west of the Portland mine, are the workings of the Granite, Dead 
Pine, and Ajax mines. Along the eastern declivity, south of the Portland, are the 
workings of Stratton’s Independence mine. 

The contact is well exposed on all the Portland levels from the 500-foot to the 
1,000-foot. As a rule it is sharp and readily determined. The breccia for a few 
inches from the granite is usually hard, rather fine grained, and, as shown by micro¬ 
scopic study, chiefly of granitic origin. It rests snugly against the rather minutely 
irregular wall of granite, which is not as a rule noticeably fractured or shattered. 
Usually there is no evidence of faulting along the contact, and there can be little 
doubt that the breccia was in the main originally deposited in the position it now 
occupies relative to the granite. Occasionally there has been some Assuring along 
planes adjacent and generally parallel to the contact. Such fissure planes, however, 
do not follow the irregularity of the actual contact and are not connected with any 
important faulting. 

On the 500-foot level a sharp contact between granite and breccia is well 
exposed in a short drift on the so-called Shaft vein, just west of the Burns shaft. 
The contact here is less steep than is common on the lower levels, dipping north at 
about 60°. It may also be well peen about 300 feet southeast of the Burns shaft in 
a crosscut east from the Portland vein. The contact is here ideally sharp, the breccia 
resting closely upon an uneven surface of granite. The dip is abnormally low, being 
only about 15° toward the east. This low dip is undoubtedly local, and if the 
breccia could be removed the granite at this point would probably be found forming 
a relatively flat bench or step, with steep scarps above and below. The contours of 
PI. XXVIII are strongly indicative of such changes of slope. 

On the 600-foot level the contact as exposed a short distance north and east 
of the Burns shaft is definite and close. It is rather irregular, but nearly vertical 
on the whole. Near the Diamond vein, however, about 300 feet east of the shaft, 
the contact is a regular plane dipping about 35° NE. and exhibiting clear evidence 
of some faulting between the granite and the breccia, but the movement is appar¬ 
ently local and not connected with any great displacement. The moderate dip, 
here as on the 500-foot level, prevails on the crest of the granite promontory. It 
is 20° steeper, however, than on the level above, which fact, taken in connection 
with what is known of the contact below, indicates proximity to the outer edge of 
the granitic bench already mentioned. 

On the 700-foot level the contact between the granite and breccia is exposed 
in the main drift about 100 feet north of the Burns shaft. It is here sharp and 


436 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


close, rather irregular, and as seen in the drift nearly vertical. East of the Burns 
shaft the contact practically coincides with the No. 2 vein. 

On the 800-foot level the contact is in part the east wall of the No. 2 vein. It 
is sharp and irregular in detail. The granite is locally shattered for a foot or two 
from the contact, which is here nearly vertical. Toward the north the contact 
soon swings westward, away from the No. 2 vein, and is again well exposed in the 
main northeast crosscut about 125 feet from the Burns shaft. This contact is 
remarkably close and definite and shows no evidence of faulting. Its course where 
cut by the crosscut is nearly north and south, and it dips about 80° E. 

On the 900-foot level the contact between the granite and breccia is exposed 
in at least five places. North of the Burns shaft the granite shows some breccia- 
tion near the contact, and the latter is not so sharp and distinct as in other parts 
of the mine. Just east of the No. 2 vein, which is partly within the granite on 
this level, the contact is clearly exposed in a short crosscut. The granite is shat¬ 
tered, but not brecciated, for a distance of 2 or 3 feet from the breccia, while the 
latter contains abundant particles of microcline and some small fragments of granite, 
those seen being less than 3 inches in diameter. The contact here dips 75° to 80° 
E. A little farther north a crosscut west of the No. 2 vein, which is here wholly 
in granite, exposes a close, definite, irregular contact of the latter rock with the 
breccia. The dip of the contact here is practically vertical. 

On the 1,000-foot level the contact is exposed about 100 feet north of the 
Burns shaft and along the No. 2 vein. In general it is approximately vertical 
and presents characteristics similar to those observed on the level above. As pre¬ 
viously noted, the lodes are not deflected when crossing the contact. 

Intimately associated with the volcanic breccia and tuff are bodies of massive 
latite-phonolite and syenite. The latite-phonolite is usually a light-gray porphyritic 
rock showing small phenocrysts of feldspar and biotite. Its petrographical char¬ 
acter is described on pages 68 to 84 of this report. The rock, when unaltered, is 
readily distinguished underground from the breccia by its more angular fracture, 
greater hardness, crystalline texture, and, in one of the masses, by the presence of 
the black, sparkling scales of biotite, which do not so far as known occur in the 
volcanic breccia. The latite-phonolite is also far less generally impregnated with 
pyrite than the breccia. But notwithstanding these differences it is always an 
exceedingly difficult matter to determine the exact contact between the massive 
rock and the breccia, owing to the fact that the latite-phonolite is itself shattered 
or brecciated near the contact and locally mineralized with pyrite. When both are 
mineralized and altered, sharp distinction is seldom, if ever, possible between 
brecciated latite-phonolite, on the one hand, and a volcanic breccia containing 
abundant particles of similar rock on the other. There is nearly always a debatable 
zone from 10 to 100 feet in width which passes on one side into less shattered mas¬ 
sive latite-phonolite and on the other into a breccia containing, besides latite- 
phonolite, particles of quartz and microcline from the granite and sometimes of 
phonolite. 

The principal occurrence of latite-phonolite is in the northern part of the mine, 
in the vicinity of the No. 3 shaft, which is practically in this rock nearly down to 
the 1,000-foot level. It forms a large mass whose shape is only partly determinable 


MINES OF BATTLE MOUNTAIN, EAST GROUP. 


437 


from the present underground development. The southern boundary of this latite- 
phonolite, on all levels, lies along the northern edge of the great Hidden Treasure- 
Captain ore zone, and there can be little doubt that the presence of the latite-phonolite 
has determined the position and particularly the northern limit of this ore zone. 
The adit level, from a point near the Wisconsin shaft, extends northward for nearly 

I, 200 feet through this body of latite-phonolite before again entering the breccia. 
It is noteworthy that the ore of the Colorado City and Hawkeye shafts occurs in the 
breccia just north of this latite-phonolite, the latter occupying the relatively barren 
ground between this ore and the Captain-Hidden Treasure ore zone. On the same 
level a west crosscut past the No. 3 shaft is entirely in this body of latite-phonolite, 
which is the prevailing rock in the vicinity of the Lost Anna shaft. The same large 
irregular mass of latite-phonolite is encountered on the lower levels just northwest 
of the Hidden Treasure and Captain stopes. The 500-foot and 1,000-foot levels, 
however, are the only ones which explore the latite-phonolite for any considerable 
distance. The distribution of the latite-phonolite on the 500-foot level, so far as 
known, is shown in PI. XXVIII. On that level a crosscut west of the Anna Lee 
shaft cuts through about 300 feet of latite-phonolite, which, as the surface map 
(PI. II, in pocket) shows, is probably an offshoot from the main body to the north. 
On the same level a crosscut west from the No. 3 shaft, after passing for about 450 
feet through latite-phonolite, is continued for about 70 feet in sj^enite. This is 
probably the same mass as that mapped on the northern slope of Battle Mountain 
(PI. II). The contact between this syenite and the latite-phonolite is indistinct, 
and the one rock probably grades into the other. 

In September, 1903, the drift north from the No. 3 shaft was about 700 feet 
in length and all in the latite-phonolite. The eastern contact of the massive rock 
with the breccia has apparently a westerly dip, for while on the adit level the latite- 
phonolite extends at least 400 feet east of the No. 3 shaft, on the 1,000-foot level 
the contact lies from 50 to 75 feet west of the shalt, which on this level is in breccia. 

The latite-phonolite (biotite trachyte) just considered is the “ mica-bearing 
andesite” of Cross," which he described as occurring on Battle Mountain, but 
omitted from his‘geological map on account of the difficulty of determining its 
exact boundaries. 

East of the No. 2 shaft and the No. 2 vein is a part of the Portland property 
that has as yet had very little underground exploration. The geological map (PI. 

II, in pocket) shows that there is exposed at the surface just east of the Burns 
shaft, stretching northeastward along the slope of Battle Mountain and eastward 
to Goldfield, an exceedingly irregular area of latite-phonolite. This phonolite is 
met with underground on the adit level, extending from the portal to a point about 
200 feet north of No. 2 shaft. In places, particularly near the shaft, it is fresh and 
approaches syenite in texture. As in the case of the andesite, its contact with the 
breccia on the northwest is obscured by shattering and mineralization, so that prac¬ 
tically nothing can be made out of the geological relation of the two rocks. Below 
the adit level the phonolite is known to occur in the old Scranton workings and on 
the 220-foot Portland level. It formed the general country rock of part of the 

a Geology and mining industries of the Cripple Creek district, Colorado: Sixteenth Ann. Rept. U. S. Geol. Survey, 
pt. 2, 1895, pp. 75-76. 






438 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

stoped-out Portland vein, but as these old upper levels are for the most part inac¬ 
cessible, it is not at present practicable to ascertain the form and extent of this 
eruptive mass. It has not been recognized on the 350-foot level, but on the 500- 
foot level a long crosscut northeast of No. 2 shaft passes for about 400 feet through 
a body of altered massive rock which is probably part of the same mass (PI. 
XXVIII). Two other levels, the 500-foot and the 600-foot, reach this latite- 
phonolite. On the 500-foot level a massive rock is exposed on the south side of the 
station of the No. 2 shaft. It is too much altered for satisfactory determination, but 
is apparently latite-phonolite. A similar altered rock occurs along the east side of a 
little drift 450 feet northeast of the Burns shaft (PI. XXVIII) and is probably part 
of the same mass. On the 600-foot level what seems to be the southern continuation 
of the same body of rock is encountered in the north face of a short drift about 500 
feet east of the Burns shaft, and apparently also in a crosscut about 200 feet east 
of the No. 2 vein. The rock on this level is in part unaltered and is clearly a latite 
phonolite. (See p. —.) It might have been expected that the same rock would 
have been cut in the long northeast (Last Dollar) crosscut on the 800-foot level. 
But this shows nothing but breccia, and it is probable that the latite-phonolite of 
this part of the mine occurs in masses of very irregular shape. 

All the large rock masses of the Portland mine are cut by numerous dikes. 
These exhibit considerable diversity of trend, but the greater number have courses 
ranging from north to N. 35° W. In other words, dikes and lodes are generally par¬ 
allel or coincide. The general arrangement of the dikes is illustrated for one of the 
most important and representative levels in PI. XXVIII. 

The most abundant dikes are those of phonolite. They range in width from 
a few inches to 30 or 40 feet, the greater number, however, being from 2 to 5 feet. 
The phonolite is invariably altered, and presents the usual appearance character¬ 
istic of this rock when occurring as dikes within the mineralized portion of the dis¬ 
trict. It is usually a pale-green aphanitic rock with a well-marked platy parting 
parallel to the dike walls. While many of the phonolite dikes are very irregular, 
changing in width, dip, and strike from point to point, some maintain a fairly 
uniform width and trend for over 1,500 feet. One of the most persistent is a nearly 
north-south dike which coincides with the No. 9 Captain vein on the north, passes 
just west of No. 2 shaft, and continues into Stratton’s Independence mine about 
600 feet southeast of the Burns shaft. It is not certain that this is really a single 
continuous dike, but it has been cut and drifted on at so many points (PI. V, p. 26) 
as to render such continuity probable. As examples of shorter and more irregular 
dikes may be cited some occurring near the No. 2 shaft on the 500-foot level and 
the dike accompanying the Portland vein. 

Besides the phonolite dikes, there are a number of “basalt” dikes. These are 
usuallv nearly vertical and have the same general strike as the phonolite dikes. 
Tliev are rarely over 6 feet in width, and fairly regular. When followed by drifts, 
they are frequently found to pinch and disappear, but a short crosscut to one side 
or the other w 11 usually reveal a second dike, which when followed soon attains 
the average width of the first and continues on the same general course. These 
dikes are invariably decomposed, so that their original petrographic character can 


MINES OF BATTLE MOUNTAIN, EAST GROUP. 


439 


be but imperfectly discovered. Some of them, as the dike exposed on the 500-foot 
level east of the Captain veins (PI. XXVIII) were olivine-feldspar basalts, pos¬ 
sibly nepheline bearing, in which the olivine has been alter d to serpentine and 
carbonates and the groundmass is full of calcite. Others, such as the Anna Lee 
dike, which passes through the Anna Lee shaft (PI. XXVIII) and is probably one 
of the dikes cut in the crosscut west of the No. 3 shaft, contained phenocrysts of 
olivine and augite lying in a groundmass rich in augite and magnetite. This 
groundmass, though obscured by calcite, apparently never contained plagioclase, 
and the rock is probably to be lassed as a limburgite. The basaltic dike shown 
on the 500-foot level (PI. XXVIII) just east of the Burns ihaft is also probably a 
limburgite. It contains a little biotite and some kernels of unaltered olivine. The 
groundmass shows abundant calcite and a clear isotropic mineral which is probably 
analcite. 

As a rule the basic dikes as encountered underground are of a dull dark- 
greenish color, so softened by decomposition as to be readily picked down and 
rapidly disintegrating on exposure to the air. The harder, fresher phases are 
nearly black and commonly reveal a regular platy jointing parallel to their walls. 
These fine parallel cracks are frequently filled with white calcite and the structure 
thereby accentuated (PI. XVI, B, p. 166). 

The basic dikes are all later than the phonolite dikes, which they frequently 
cut. Whether the feldspathic basalts are earlier or later than the limburgites is 
not known, though it is probable that both belong to the same general period of 
eruption. 

LODE SYSTEMS. 

The Portland mine contains more productive lodes and presents greater variety 
in the character of its ore bodies than any other mine in the district. By far the 
greater number of the lodes have courses lying between north and N. 35° W. In 
general the more nearly north-south strikes prevail in the southern part of the mine, 
near the Burns shaft, while the more westerly strikes are characteristic of that part 
of the mine lying just north of the No. 2 shaft. The only notable exception to the 
foregoing general statements is that furnished by the Bobtail vein, which strikes 
about N. 60° W. A number of the lodes are practically vertical: others have a 
westerly and some an easterly dip. The dips as a whole are high—rarely under 70°. 
The Bobtail, however, has a southwesterly dip of a little less than 65°. The ground 
which has hitherto proved most productive in the Portland mine lies in two broad 
vertical zones which cross the general strike of the lodes nearly at right angles. One 
of these northeast-southwest zones crosses the lode systems at the Burns shaft, and 
contains the productive portions of the Portland, Bobtail, Diamond No. 2, Rose, 
and Scranton lodes. The width of this zone is not susceptible of accurate meas¬ 
urement, but one boundary may be considered as passing about 300 feet northwest 
of the Burns shaft. The other boundary probably lies between 1,100 and 1,200 feet 
southeast of the Burns shaft and includes the productive ground north of the 
No. 1 shaft of Stratton’s Independence mine, as well as that of the Strong, Dillon, 
and Monument mines. Such lodes as pass from granite into breccia, or vice versa, 
cross the contact between these rocks without noticeable deflection. 


440 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

The second zone lies northwest of a line passing through the Portland No. 2 
shaft and the old Anna Lee shaft. Its width is approximately 600 feet and it 
includes the productive portions of the Lee, Hidden Treasure, and Captain veins. 

Inspection of the map (PI. II, in pocket) shows that the existence of these two 
main zones, separated by a comparatively barren zone from 150 to 200 feet in width, 
is a prominent feature of the Portland mine. It is very doubtful, however, whether 
these same zones are persistent and can be recognized in the properties adjoining 
the Portland on the west and east. A long west crosscut and a long northwest 
drift on the Anna Lee basaltic dike, both on the 500-foot level, have failed to find 
any southwest continuation of the remarkable zone in which occur the Captain and 
Hidden Treasure ore bodies. In view of this fact the term zone is perhaps some¬ 
what misleading. The relation of the ore bodies to the mass of the country rock 
might be expressed bv saying that the ore bodies are not distributed generally 
through the latter, but are clustered together in huge, nearly vertical cores. These 
rock cores, within which the lodes are productive, are separated from the surrounding 
relatively barren country rock by rather indefinite boundaries. Their horizontal 
sections are irregular, but are generally elongated in a northeast-southwest direc¬ 
tion, so that in a limited area they have the appearance of zones. 

None of the productive lodes of either of the Portland zones has yet been traced 
into the other zone. The No. 2 and Diamond veins, so productive in the southern 
zone, are not recognized in the northern zone, nor are the numerous and rich lodes 
collectively designated the Captain system known south of the No. 2 shaft. 

The original Portland vein, sometimes erroneously supposed to be the same as 
Stratton’s Independence vein, has been developed in the southern part of the mine, 
and lies just east of the Burns shaft. Its course on the whole is nearly north and 
south, but it is distinctly curved, striking in its northern part a little east of north 
and in its southern part about S. 25° E. It dips at an average angle of 70° to 75° W. 
The Portland vein is not distinct on the 600-foot and lower levels. 

The Bobtail vein strikes about N. 60° W. and dips about 65° SW. This lode 
and the Portland vein cross without any observable displacement of one lode by the 
other. The Bobtail as a rule is a regular, well-defined lode, which outcrops at the 
old Bobtail shaft and crosses the Portland vein on the surface near the portal of the 
adit level. Southeast of its intersection with the Portland vein the Bobtail is not 
very well defined until the 600-foot level is reached. Below this the Portland vein 
in turn dies out or becomes unrecognizable. 

The Diamond veins comprise two or more rather short, generally parallel fissure 
zones lying 225 feet east of the Portland vein. These lodes strike about N. 10° W. 
and dip steeply to the west. The Diamond veins have not been identified with 
certainty on the 500-foot and higher levels. 

The most easterly lode of the southern ore zone is the important No. 2 vein, 
which strikes from N. 20° to 25° W. and is clearly the northern continuation of the 
Independence vein of Stratton’s Independence mine. Unlike the other lodes of 
this zone, the No. 2 vein dips easterly at an angle of 70° to 75°. It is indistinct 
and of no importance above the 500-foot level, but is well marked on the 600-foot 
and lower levels. The so-called Scranton and Rose veins of the 700-foot and 
800-foot levels appear to be merely northern continuations of the fissure zone of the 


ELEVATIONS ABOVE SEA LEVEL 


U S-GEOLOGICAL SURVEY 


PROFESSIONAL PAPER NO.54 PL XXIX 





10000 - 


9900 


-^^7 • v - « - . a 

h- 

i: I 

* 

: --v f : a-, 

. ■ V ■ i': % 




9800 -f 


9700 



'O /' \ , a; -stir.'. 

-1' -'. - iV. , 6.// • 







.“.r- ^-vr - = - v • ,y . 

-j—^ it* r n— '/ ~ ' /' <r// ■ «, < 

- ■ : - -/' ;•//■, : / aV ■ 7 ix?: ... . 

• /< m • •/ ^Sk# • • • ■» ■ : > W 

Jr /r A 

, // ' ./<*>,/ ■ \A U ■ 

/ J-f ^ 

, v ■ r# ■ , - If ■ ' 

< „ / ■ aT#R N93 LEVELJOF: <o V 

ft ’ &// » * > •« o 

,// P NO 4LEVEL 

-■■ t o 'i « 

7 / ' ‘ 'X#' ‘ ' 

V/ . // 

>. ■ •» Jar - . v>u - . .«• ■ ,. 

R N?5 /Jf LEVEL 

tfl. V ■ ■ *>■ , ■ 

■ . • ■ j :• 


... // \ 

j. Si 

// 5? ’ ■ - - •- 



9500- 



9400 


\^«r'i '- s 1 • t - 

_f/-' ( 'l-' W »'0xVi‘.;3 

V/ 1 /-I r- / ' V-T ' r ; ' 7s ' V ^s'l 1 SJE.70Q-FT LEVEL 

|/c i^i /'.-r ' i-' ; > 1 'm - i'x^\rs>7j 7 v'' 


9300 



FT.^ilLEVEL „ 




/i/'- li - " ' I ; ; 

||| ■ PN96 LEVEL • ■ 

. . U ' 1 ;/ '? 

I y. ' M *•*?' ; r ■ 

• -'f l Erl- - S? 1 la *r 

. • u • •••- iJ fsl , i ? • ■ i j .* 


8 I;' i. • . * - :.. - 6 :- ■• ■;••■ 

| . 
f>4 v u -7-t : / 4 • ‘% 

j - ' ° ‘>i ' ‘ • ‘ •« • 

h ■ 

!#• :,■:■■ ■■:■■■.■»;-■■ ;■•.■• ■; :\o 

1 | 

, \L-^v 

'I ' Z/i / 

■■ii u U' j . • ' 

i’ -,. 

. ..../*■.’ .. 

O' i < 

w". > * £' 

-rn, 

f - A. 

• -7 Ixvl. - ‘ 1] 


■ 





i 


. i 1 \ • c : ^ 

V. / \l 

■ sjp ■. ■ .■. t 

v - o.* J ’• :> 

■ / V- • 


9100 - 



9000- 



VERTICAL SECTION THROUGH THE BURNS SHAFT, PORTLAND 
MINE, SHOWING BRECCIA CONTACT, VEINS, AND DIKES 

AFTER V. G. HILLS 
Scale 

o 100 200 3 oo feet 


Basalt dikes Phonolite dikes Veins 


19 0 5 


Slopes 


:v i s i - 

Granite 


UCA'V;! 

Breccia 


T7! 

m 


Dump 



JULIUS BIEN & CO N V 


































































441 


MINES OF BATTLE MOUNTAIN, EAST GROUP. 

No. 2 vein. (See PI. XXVIII, p. 434.) The relation of the lodes of the southern zone 
in the Portland mine to those of Stratton’s Independence mine is discussed in the 
description of the latter mine on page 452. 

The northern ore zone of the Portland mine comprises a large number of approxi¬ 
mately parallel, nearly vertical fissure zones, which are often so closely spaced and 
so connected by branching fissures as to render their identification extremely difficult 
unless continuity is demonstrated by continuous drifts or stopes. Names were 
originally given to the more prominent fissure zones as they were encountered on 
various levels, but it was found upon further development that these lodes are often 
accompanied by adjacent nearly parallel lodes, which, though they may be of no 
importance on one level, may contain valuable ore bodies on another. Such addi¬ 
tional lodes were distinguished by prefixing numbers to the name of the original. 
Thus, for example, there are the No. 3 Hidden Treasure, the No. 4 Lee, and the No. 9 
Captain veins. The general strike of the lodes of the northern ore zone, as may 
be seen from PI. XXVIII, is regular and seldom varies more than a few degrees 
from N. 35° W. The dip, as nearly as can be determined in lodes so close together 
and often distinct only for short distances, is on the whole about vertical. 

The most southwesterly lodes of this zone are the four Lee veins, numbered from 
southwest to northeast and lying just east of the old Anna Lee shaft. These are 
rather short lodes of not very regular strike. Nos. 1, 2, and 3 have the prevalent 
strike of N. 30° to 35° W. The No. 4 Lee, however, strikes N. 65° W. and dips about 
75° NE. This, the most easterly of the four Lee veins, has great vertical persistency 
and is recognized on all the levels from the adit down to the 1,000-foot level. It is 
more nearly vertical than most of the lodes of the northern ore zone. 

North of the Lee veins are the No. 1, No. 2, No. 3, and No. 4 Hidden Treasure 
veins. These constitute a zone of generally nearly parallel fissures, ranging on 
different levels from a single narrow fissure to a total width of about 100 feet on 
the 900-foot level, where four individual zones of Assuring are recognized. The 
general strike of the Hidden Treasure veins is about N. 30° W. They thus join 
the more westerly No. 4 Lee vein at their southern ends. Inspection of PI. XXVIII 
shows that the Hidden Treasure fissure zones align with the No. 2 vein of the 
southern ore zone, but so far as known there is no connection*of the lodes across 
the intervening barren ground. While the No. 2 vein dips, as we have seen, 
to the northeast, the Hidden Treasure veins are, on the whole, approximately 
vertical. The Hidden Treasure veins are of but little value above the 500-foot 
level. On that level the No. 1 Hidden Treasure, and on the 600-foot level the 
No. 2 Hidden Treasure also, attain economic importance, which they maintain 
down to the 800-foot level, where the No. 3 Hidden Treasure becomes the prominent 
lode of the system and so continues to the bottom of the mine. 

Immediately northeast of the Hidden Treasure veins is an extensive series 
of parallel fissure zones known as the Captain system. The general strike of these 
fissures is N. 35° W. and they are, on the whole, nearly vertical. They constitute a 
broad sheeted zone from 400 to 500 feet in width, which is not sharply distinguished 
from the Hidden Treasure veins. Both sets of lodes belong, in fact, to one great 
zone of parallel Assuring. Within the Captain system are distinguished nine 
principal lodes, numbered from southwest to northeast. But these lodes are not 


442 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

equally distinct on different levels and there is often much minor Assuring of the 
country rock between them. It is therefore by no means certain that the same 
number is always applied to the same lode on different levels. For example, the No. 
4 Captain vein on one level may correspond to what is termed the “ No. 5 ” Captain 
vein on another. The designations of these lodes are frequently changed as develop¬ 
ment throws new light on their relations. The easternmost productive lode of the 
series, the No. 9 Captain vein, presents an exception to the general strike and dip 
of the other lodes of the Captain system and is associated with a phonolite dike. 
This lode strikes a little east of north and dips west at about 80°. It probably 
should not strictly be included within the Captain system. 

The Captain veins, while economically of great importance, as will be later 
shown, are not persistent. They have rarely been followed horizontally for more 
than 300 feet. First attaining importance between the 220-foot and the 350-foot 
level, the known lodes of the system become indistinct and of comparatively little 
value below the 600-foot level, though some ore occurs in them above the 700-foot 
level. 

North of the great ore zone in which occur the Lee, Hidden Treasure, and 
Captain veins is an extensive territory now being exploited from the No. 3 shaft. 
Thus far no ore bodies of importance have been discovered in this part of the 
Portland workings proper, though ore was formerly shipped from the old workings 
of the Colorado City and Hawkeye shafts nearer the surface. About 225 feet 
southwest of the No. 3 shaft, however, is the Lost Anna vein, striking northwest 
and southeast and dipping steeply to the northeast. Tins lode, which lies in the 
general line of the Captain veins, is known on the adit and 1,000-foot levels. While 
apparently not of much importance on the upper level, it promises well below the 
1,000-foot level. 

CHARACTER OF ORE. 

Probably no one mine in the Cripple Creek district has during its history pro¬ 
duced more varied types of ore than the Portland. All the unoxidized ores, 
however, are alike in owing their value to the presence of a telluride of gold, which 
seems to be almost invariably calaverite, though the occurrence of sylvanite has 
been reported by Rickard . h This telluride is rarely found in well-formed crystals and 
is frequently present in particles so minute as to be invisible to the naked eye. 

The chief contrast as regards texture and general mineralogieal association 
of the ores is to be found between those occurring in granite, on the one hand, and 
those found in breccia or phonolite, on the other. 

The ores in the granite are of distinctly metasomatic origin. The alteration 
of the country rock is always more or less closely related to Assuring, though the 
Assures are in some cases microscopic. The change from altered to unaltered rock, 
while never sharp, may take place within a distance of a few inches. The most 
striking characteristic of the altered rock is a porous texture and a loss of more or 
less of the reddish tint of the unaltered granite. Closer examination shows that 
while the original porphyritic aggregates of pink microcline may remain, the rest 
of the rock, consisting originally of microcline, oligoclase, quartz, and biotite, may 


a Rickard, T. A., The Cripple Creek gold field: Inst. Hin. and Met., London, vol. 8, 1899. 






MINES OF BATTLE MOUNTAIN, EAST GROUP. 


443 


be completely recrystallized as a porous, vuggy aggregate of valencianite (secondary 
orthoclase), quartz, fluorite, occasionally a little calcite, pyrite, calaverite (rarely 
visible), and sometimes a little sphalerite and galena. Ore of this type was formerly 
of much greater importance in the Portland mine than now, and was stoped in 
large quantities from the Diamond veins. 

The ore at present most typical of the mine is that occurring in breccia, par¬ 
ticularly in the Captain stopes. This consists of fine-grained gray breccia, con¬ 
taining much finely disseminated pyrite and considerable scattered carbonate, 
which appears to be in most cases dolomite rather than calcite. The calaverite 
occurs in very narrow fissures or joints in this breccia, associated with crystalline 
films of dolomite, with sometimes a little quartz and fluorite. In most places the 
ore shows very little calaverite to the naked eye; but in some of the richer stopes 
the rock, when split open along these joints, reveals an abundance of thin-bladed 
crystals of silvery calaverite that are occasionally 2 inches in length and frequently 
form branching or stellate groups. These crystals are often accompanied by a 
little molybdenite. The value of the ore appears to lie wholly within the narrow 
joints which are seldom individually large enough or persistent enough to be dignified 
even with the name of veinlet. The fine pyrite impregnating the breccia is not 
known to be auriferous, though samples of pyritized breccia often contain $2 to S3 
per ton in gold. The ore of the Hidden Treasure veins has crystallized in larger 
and more open fissures than the Captain ore and gangue minerals are consequently 
more conspicuous. The calaverite occurs with dolomite (often in well-developed 
rhombohedrons), fluorite, and quartz. 

The Lost Anna and Lee veins are characterized by more open Assuring and 
more abundant vein matter than most of the productive Cripple Creek veins. 
They contain abundant pyrite, and in some places galena and sphalerite, associated 
with dolomite, quartz, and fluorite. Calaverite occurs usually in the porous or 
vuggy portions of the vein, and in the Lost Anna vein is sometimes associated , 
with roscoelite. 

The ore of the Anna Lee chimney was soft and oxidized down to the bottom 
of the worked-out ore shoot. 

PAY SHOOTS AND LODE STRUCTURE. 

With the exception of the so-called Anna Lee chimney, all of the ore of the 
Portland mine occurs in the form of lodes; that is, in nearly vertical deposits of 
essentially tabular form. The general plan and distribution of these lodes has 
been already described. Some account will now be given of the shape and structure 
of the ore bodies themseHes. 

Three important types of ore bodies have been recognized: (1) Deposits along 
fissure zones in breccia, (2) deposits along fissure zones in granite, and (3) mineral¬ 
ized phonolite dikes. These three classes are not always distinct, for, as will 
presently be shown, deposits of the third class are not infrequently combined with 
deposits belonging in the first or second class. 

In the first class belong the first eight Captain, the three Hidden Treasure, 
and the four Lee veins of the northern ore zone and a portion of the No. 2 vein 
in the southern zone. These lodes are sheeted zones of varying width, definiteness, 


444 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


and persistency. An excellent example of the more persistent and well-defined 
mineralized zones of sheeting is the No. 3 Hidden Treasure vein, as developed 
on the lower levels of the mine. Just above the 1,000-foot level this lode has a 
pay shoot about 500 feet in length, with an average width of about 12 feet. In 
the wider parts of the lode the Assuring is rather irregular. There are generally 
two or more nearly parallel and approximately vertical fissures, the outer ones 
being 6 to 10 feet apart. Between these the breccia is traversed by cracks running 
in all directions. The best ore occurs in the main vertical fissures, which are 
mere cracks in the rock, usually less than an inch in width, with a lining or vuggy 
filling of fluorite. There are no definite walls to the lode, the rock outside of the 
main vertical fissures being also irregularly jointed and carrying gold for varying 
distances from the main fissure zone. Where the stoping width of the lode, which 
is in some cases 15 feet, narrows to 10 feet or less the sheeting of the rock is more 
regular and more conspicuous. Such parts of the lode frequently exhibit in the 
neighborhood of 20 rather regularly spaced narrow parallel fissures with nearly 
vertical dips. Those sections of the lode in which such regular sheeting occurs 
are usually of higher grade than the wider and less regularly fractured portions. 

The other lodes in the breccia are all generally similar in structure to the 
Hidden Treasure lode. Some, such as the Lee veins, are narrower and often 
more sharply differentiated by their narrow-spaced vertical Assuring from the 
country rock. Definite vein walls, however, do not occur. Occasionally, as in the 
No. 1 Lee vein just above the 800-foot, level, the sheeted structure passes into a 
less regular form of reticulating fractures suggestive of what are commonly known 
♦ as stringer lodes. Other lodes, such as those composing the Captain group, are 
even less distinctly differentiated from the country rock than the Hidden Treasure 
lode. While vertical sheeting can sometimes be recognized in the medial portions of 
the Captain veins, the existence of the lode-is often marked merely by the irregular 
fracturing and jointing of the breccia. Such fracturing frequently involves all of 
the rock intervening between the indistinct medial planes of two or more of the 
Captain veins, and the fractured rock constitutes practically a single large ore body 
which is stoped as a whole. Such is the great stope 120 feet wide, on the Nos. 
3, 4, 5, and 6 Captain veins above the 350-foot level. In these large stopes it is 
often difficult or impossible to recognize an} 7 linear system of fissures such as might 
properly be called a lode. Practically all the minute fractures in the breccia con¬ 
tain telluride of gold, often invisible, but sometimes occurring in thin sheets of 
flat radial aggregates of sylvanite or calaverite along fissures a small fraction of 
an inch in width, and revealed by splitting the breccia along these veinlets. Such 
lodes pass gradually and indefinitely into the country rock, the limits of the ore 
body being determinable by assays alone. 

The lodes in the breccia are not all equally persistent, nor is persistency always 
commensurate with the size and importance of ore bodies. The largest ore body, 
about 500 feet in length, is found in the No. 3 Hidden Treasure vein. Tins lode, 
however, is not certainly known above the 600-foot level, whereas the smaller No. 4 
vein has been stoped almost continuously from the surface to the 1,000-foot level. 

In the Captain group of lodes the largest ore body is something less than 300 
feet in length, and most of those discovered are shorter than this. These lodes 


MINES OF BATTLE MOUNTAIN, EAST GROUP. 


445 


first attained importance between the 220- and 350-foot levels, and have been very 
productive near the 350-foot level. Below the 600-foot level, while the Captain 
Assuring continues, the ore is of low grade, and on the 1,000-foot level such indistinct 
Assuring as persists is associated with but little more value than is found in the 
breccia country rock, most of which in this part of the mine affords assays up 
to S3 in gold per ton. The Xo. 1 Hidden Treasure vein, while recognized on the 
350-foot level, first becomes important between this level and the 500-foot, and 
has been stoped down to the 900-foot. The Xo. 2 Hidden Treasure has been 
productive from the 600-foot to the 800-foot level, while the Xo. 3 Hidden Treasure, 
first stoped above the 700-foot level, has maintained its importance to the bottom 
of the mine. 

Owing to the uncertainty attaching to the identification of individual members 
of these closely spaced Hidden Treasure and Captain groups on different levels, 
the foregoing statement as to the vertical distribution of the various pay' shoots 
may be modified in the course of future underground development. But enough 
is known to bring out the essential fact that the pay shoots in the various bodies 
do not as a rule possess great vertical persistency and may occur at all depths thus 
far explored. There are pay shoots known in depth which do not reach the surface 
and there are pay shoots known at the surface which do not extend to great depth. 

In the southern ore zone the Xo. 2 vein and its branches are the only lodes 
which are of much importance within the breccia. This lode is not definitely 
recognized on the 350-foot level, though a lode stoped above that level and called 
the Diamond vein is probably really the Xo. 2 vein, the Diamond vein proper 
apparently never having been recognized in the breccia above the 600-foot level. 
Between the 500- and 800-foot levels the ore bodies of the Xo. 2 vein have been 
stoped to a width of 40 and occasionally of 60 feet, up to the Stratton’s Independence 
line. The width of this ore is subject to sudden changes, a narrow sheeted zone 
of pay ore 4 to 5 feet wide expanding within a few feet to a width of 50 feet and 
again as abruptly contracting. The wider ore bodies occur near the 600- and 700-foot 
levels, the pay shoots being generally narrower on the lower levels. Toward the 
north the lode appears to split, the Rose and Scranton stopes on the 700-foot level 
being probably on branches of the main zone of Assuring, known as the Xo. 2 vein. 

Lodes formed by mineralization along fissure zones in granite are well exempli¬ 
fied by the Diamond vein and by portions of the Xo. 2 vein. In the granite the 
fissures which served as channels for ore deposition are less conspicuous than in the 
breccia. In the latter rock the valuable constituents of the ore are practically con¬ 
fined to the fissures themselves. Xot so in the granite. Here metasomatism has 
been more active and ore minerals, among which fluorite and pvrite are usually most 
conspicuous, occur distributed through the mass of the rock, in many instances for 
20 or 30 feet from the main fissure zone. As a result of this action, the ore bodies 
are usually of very irregular shape. As a rule there is little or no waste mixed with 
the ore, whereas in the breccia the rock between the joints or fissures is invariably 
worthless. At varying distances from the main fissure zone which was the deter¬ 
minative factor in the formation of the ore body the ore changes to unmineralized 
granite. In some cases the change is abrupt, in some gradual, but only under 
exceptional circumstances is there a distinct wall separating country rock and ore. 

13001 — No. 54—06 - 30 


446 GEOLOGY AND GOLD DEPOSITS OF THE CRTPPLE CREEK DISTRICT. 

The great Diamond ore body, which about the year 1896 furnished the bulk of 
the ore from the Portland mine, had a maximum width of fully 50 feet and a length 
of about 100 feet. This ore body extended from a point just above the 600-foot level 
nearly to the 1,000-foot level. Above the 600-foot level the ore ended abruptly at 
the contact of the granite with the overlying breccia. Between the 600- and 700-foot 
levels the ore body w r as divided by a huge horse of granite, on the east side of which 
the bulk of the ore lay. The collapse of this horse, after the removal of the ore ; 
formed a great chamber now well seen from the 700-foot level. 

The body was largest between the 700- and 800-foot levels, and averaged over 
$100 of gold per ton as shot down in the stope, while several carloads of ore mined in 
1899 just above the 600-foot level carried over 30 ounces of gold per ton. On the 
900-foot level the ore was usually less than 10 feet in width and had fallen in value to 
an average of about $25 per ton. Below this level the ore barely paid for extraction, 
and just above the 1,000-foot level ended rather abruptly, in many cases apparently 
at inconspicuous, nearly horizontal joint seams in the granite. On the 1,000-foot 
level the Diamond vein is represented by two sheeted zones in the granite, both 
accompanying phonolite dikes. These zones have a maximum width of about 4 
feet and are approximately 50 feet apart. These fissures are accompanied by pyrite 
disseminated through the sheeted granite, but contain no ore. The phonolite dikes 
visible on the 1,000-foot level are said to have occurred irregularly in the ore body 
above, but the ore itself was always in the granite, never in the phonolite. 

The best example in the mine of an ore body formed by the mineralization of a 
phonolite dike is the original Portland vein. It is essentially a sheeted zone which 
was most productive where it coincided with the dike. At the adit level the general 
country rock is latite-phonolite and the lode is apparently in the same rock down to 
the 220-foot level. On the 350-foot level the Portland dike and vein are in breccia. 
In the present condition of the old stopes no satisfactory study of the lode is practi¬ 
cable. The ore body seems to have been irregular in width and usually to have had 
well-defined walls—those of the phonolite dike. The lode was stoped almost from 
the surface nearly down to the 500-foot level. On this level the lode has left the 
phonolite dike and is in granite. The granite adjacent to the rather indistinct 
fissure zone is metasomatically altered and has the porous texture characteristic of 
granitic ore. It is not, however, of sufficient value to pay for extraction. 

The Bobtail vein, one of the most regular and persistent lodes in the mine, was 
studied only on the 500-foot and lower levels, where it is mainly within the granite, 
southwest of the Burns shaft. It was there seen to be of an entirely different type 
from any of the lodes just described. As a rule the lode shows considerable oxidation 
even down to the 900-foot level and its character is thereby somewhat obscured. It 
strikes nearly northwest and southeast and dips southwest. The Bobtail and 
Portland veins cross without any apparent faulting and most of the Bobtail ore 
occurs on the west side of the Portland vein and within a distance of 100 feet from 
the intersection. Smaller bodies, however, occur in other parts of the lode, as near 
the contact of the granite with the breccia, at about the 500-foot level. The rather 
irregular Assuring of the Bobtail lode follows what at first glance appears to be a 
narrow, irregular dike of some darker rock than the granite. Closer examination of 
the so-called Bobtail dike suggests, however, that it is a breccia containing fragments 


MINES OF BATTLE MOUNTAIN, EAST GROUP. 


447 


of granite. This is confirmed by the microscope, which shows the material to con¬ 
sist chiefly of finely comminuted microcline and quartz, evidently derived from the 
granite, with usually a little secondary quartz, fluorite,-and pyrite. No volcanic 
fragments were detected in this material. The Bobtail vein is therefore a fissure zone 
which follows not a dike, but an 
older fissure filled with brecciated 
material. This original fissure 
probably dates from the volcanic 
period, but whether it was filled, 
like the great crater, with particles 
which had previously been blown 
into the air, or by the trituration 
of the wall rock by movement along 
the fissure, could not be deter¬ 
mined. The breccia of the fissure 
apparently passes without break 
into the breccia filling the throat of 
the old Cripple Creek volcano. 

Another deposit, unique in the 
Portland mine, and indeed in the 
district, is the Anna Lee chimney 
or stock. No work has been done 
on this deposit for years and little 
can be added to the descriptions 
given by Penrose" and later by 
V G. Hills. 6 

Mr. Hills says: 

This ore chimney occupies the pipe or neck 
of an extinct mineral spring. It follows one of 
the main basalt dikes and extends downward, 
as far as yet followed, some 1,130 feet. It 
has several remarkable features. It is nearly 
circular in plan and varying from 15 to 30 
feet in diameter, and extends nearly vertically, 
but with a sort of a corkscrew form, into the 
earth. The ore filling this pipe consists of 
well-rounded pebbles cemented together with 
material which is composed, for the most part, 
of the same rock pulverized. This ore con¬ 
tains from 9 to 15 per cent of lime and 7 per 
cent iron, thus differing from any other ore 

body in the district. It is also a remarkable feature that the gold values contained in the pebbles and in the 
cementing material are about the same. The values are distributed with remarkable evenness through the 
mass, thus forming a notable exception to the rule of gold deposits. 

Mr. Hills gives a stereogram of the Anna Lee ore shoot, which is reproduced 
in fig. 58. 



Fig. 58.—Stereogram of Anna Lee ore chimney. (After V. G. Hills.) 


a Mining geology of the Cripple Creek district, Colorado: Sixteenth Ann. Rept. U. S. Geol. Survey, pt. 2,1895. pp. 205-207. 
5 Eighth Ann. Rept. Portland Gold Mining Company, 1902. 



























448 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

This remarkable ore body was mined down to a point above the present 900- 
foot level of the Portland mine, where the ore ceased. The old stope is at present 
accessible only on the 800-foot level. Here the ore body was roughly circular in 
plan and about 25 feet in diameter. The basalt dike has an average width on this 
level of 4 to 5 feet, but at the chimney expands to the east in an irregular swell and 
attains a local width of 15 to 20 feet. It is in this short swell and in the immediately 
adjacent breccia that the ore occurred. Just at this point the No. 1 Lee vein comes 
into the dike from the east, the ore body occurring at the junction of dike and lode. 
The less decomposed portions of the basalt, petrographically described on page 93, 
contain no ore, but much of the rock is traversed by numerous reticulated cracks 
along which decomposition and oxidation has proceeded, causing the rock to super¬ 
ficially resemble a breccia. This material is in part ore. The bulk of the ore on this 
level, however, seems to have occurred in the breccia alongside the dike at the junc¬ 
tion with the No. 1 Lee vein. This breccia contains abundant particles of microcline 
from the granite, is impregnated with pyrite, and is rather soft. It shows much oxida¬ 
tion, which penetrates the mass of the breccia very irregularly, with usually a sharp 
line between oxidized and unoxidized material. Nothing was seen on this level of 
the rounded pebbles referred to by Mr. Hills. The relation of the No. 1 Lee vein 
to the ore body on the 800-foot level strongly suggests that the vertical chimney- 
like character of the deposit may be due to the intersection of the basalt dike with 
the No. 1 Lee vein, but on the 500-foot level the lode known as the No. 1 Lee does 
not reach the dike at the Anna Lee chimney. It is probable, however, as Penrose 
suggests, a that better exposures would reveal on all levels the connection of the ore 
body with one or more fissures intersecting the dike. 

VALUE OF THE ORE. 

The average value of the Portland ore from 1894 to 1904 is shown in the table 
on page 171. It ranges from a maximum of $70.78 a ton in 1894 to $26.03 a ton in 
1902. Some of the best ore in the past came from the Diamond stopes in the granite. 
Large bodies of this ore near the 700-foot level were practically free from waste and 
averaged $100 to $150 a ton as shot down in the stopes. On the 900-foot level the 
tenor of the ore fell to about $25 a ton, and near the 1,000-foot level, where stoping 
was in progress at the time of visit, the ore shoot was barely paying $15 to $20 a ton. 

On the Hidden Treasure No. 3 stope, above the 1,000-foot level, about one- 
fourth of the rock broken is left in the stopes as waste. About 35 per cent of the 
material hoisted is screenings, with an average value of about $50 a ton. The 
remaining 65 per cent of coarse material is sorted to ore having an average tenor of 
about $20 a ton. 

While some very rich ore is sometimes found in the Captain stopes, these bodies 
are notable rather for their size than for unusual richness, and the ore as mined is 
probably not ver}^ different in tenor from the general average of the mine. 


a Sixteenth Ann. Rept. U. S. Geol. Survey, pt. 2, 1895, p. 207. 





MINES OF BATTLE MOUNTAIN, EAST GROUP. 


449 


UNDERGROUND WATER. 

According to Mr. V. G. Hills,® from whose reports most of the following facts 
in regard to the underground water of the Portland mine are taken, the first water 
was reached at a depth of 630 feet in the Burns shaft, or 9,452 feet above sea. This 
was 117 feet lower than the first water of Stratton’s Independence mine. The dis¬ 
charge did not exceed 300 gallons a minute until a depth of 704 feet was reached, 
when it rapidly increased to 700 gallons a minute. In 1896, 1897, and during the 
first half of 1898 no record of discharge was kept. In the summer of 1899 the Port¬ 
land was pumping an average quantity of 1,180 gallons a minute from a depth of 
792 feet, or an elevation of 9,290 feet above sea. At this time the Elkton mine, 
three-fourths of a mile to the northwest, was dry at 9,243 feet elevation, or 47 feet 
lower than the pumping level of the Portland. In January, 1903, the Portland 
water, which had been allowed to rise above the 1,100 foot level, remained stationary 
at an elevation of 9,005 feet, or at a depth of 1,084 feet. It then stood 13 feet higher 
than the water in the Elkton mine. In August, 1903, the water in the Portland had 
receded to a point 86 feet below the 1,000-foot level and was falling at the rate of 
2 or 3 inches a week. At this time Stratton’s Independence, the Strong, Gold Coin, 
and St. Patrick mines were all pumping and keeping their water levels below that 
of the Portland. The difference amounted to 562 feet in Stratton’s Independence, 
133 feet in the Strong, 240 feet in the Gold Coin, and 90 feet in the St.' Patrick. 
That the Portland water should recede so slowly under these circumstances is a 
remarkable illustration of the comparative impenetrability of the granite to under¬ 
ground water, even when, as in the case of the Portland and Stratton’s Independence 
mines, adjoining mines are on the same zones of Assuring. 

The influence of the El Paso tunnel on the water level in the Portland mine we 
have been unable to learn. 

STRATTON’S INDEPENDENCE MINE. 

INTRODUCTION. 

Stratton’s Independence mine lies immediately south of the Portland mine, a 
short distance northeast of Victor. It is one of the oldest, and probably the most 
famous, of the Cripple Creek mines. It is owned by the Stratton’s Independence 
(Limited), a London company with an authorized capitalization of £1,100,000. The 
property comprises 14 claims and forms a compact group covering 110 acres. Over 
400 men were employed prior to the strike of 1903, and the average amount of 
crude ore hoisted daily in 1902 and the first half of 1903 was about 630 tons, of 
which about 40 per cent was shipped after sorting. Since the time of visit the 
company has ceased direct operations and the mine is now worked by lessees. 

The mine has an interesting history. In 1891 Winfield Scott Stratton, who, 
though a carpenter by trade, was also a keen and well-informed prospector, was 
searching for cryolite on the west side of Pikes Peak. Hearing of Womack’s dis¬ 
covery in Poverty Gulch, Stratton turned his attention to Cripple Creek, and in 


a Ninth Ann. Rept. Portland Gold Mining Company, 1903, pp. 86-89. 





450 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

June examined and sampled the indistinct outcrop of the lode now known as the 
Independence. His samples were assayed in Colorado Springs, and, though the 
results were not encouraging, Stratton, impelled by a happy inspiration, rode up 
to Cripple Creek and on the 4th of July, 1891, staked out the Washington and 
Independence claims. He began work on the Washington, the southern of the 
two claims, and gave a bond and lease on the Independence, which he at that time 
regarded as the less promising property. Fortunately for him the bond was never 
taken up and he thus retained the claim which, with near-by claims subsequently 
acquired, yielded him during the next few years a profit of over $2,000,000. The 
Washington claim, lying within the granite, produced considerable ore near the 
surface, but was soon surpassed by the Independence, lying partly within the 
breccia. In September, 1894, the Independence shaft was 70 feet deep, and during 
the preceding month shipped 800 tons of ore, of which the lowest carload contained 
3? ounces of gold per ton. This ore was hoisted by a horse whim, and the mine 
was already regarded as the richest in the camp. Machinery was soon installed, 
and when Penrose made his examination in the latter part of 1894 the shaft was 
200 feet in depth. In January, 1895, a depth of 300 feet had been reached and a 
flow of 25 gallons of water a minute encountered. In March, the daily output had 
risen to about 90 tons of ore, carrying from 8 to 15 ounces of gold. It was then the 
most profitable mine in the district, though the Portland was shipping a slightly 
greater tonnage. Development proceeded steadily, and in 1897 the main shaft 
was 900 feet in depth. Negotiations for the sale of the mine were begun about 
this time, and in 1899 the property, after a comprehensive examination and report 
by T. A. Rickard, was purchased by the Venture Corporation (Limited), of London. 
In his report Mr. Rickard stated that the mine up to the end of 1898 had produced 
41,694 tons of ore, of a gross value of $3,837,359, affording its owner a profit of 
$2,402,164. The stopes aggregated 370,570 cubic feet, no less than 35 per cent 
of the entire output having come from development work in levels, winzes, and 
raises. The ore reserves were estimated by him at 70,000 tons, of a gross value 
of $6,712,000 and of an average gold content of 4f ounces per ton. He further 
expressed his opinion that fully $8,000,000 would be extracted from the ground 
already developed. Mr. Stratton was paid by the issue to him of 1,000,000 shares 
at £1 each, from the sale of which by the Venture Corporation he is reported to 
have realized about $10,000,000. On May 1, 1899, the property passed into the 
hands of its present owners. 

New hoisting machinery was soon installed and a very active attack made on 
the ore reserves by the new company. L T nder the advice of Mr. John Hays Ham¬ 
mond the shaft was sunk to 1,430 feet and extensive exploratory work done on the 
lower levels, without, however, revealing any ore bodies comparable to those 
known above level 9. Although the mine has continued to produce heavily up to 
the date of writing and has supplied ore of a gross value considerably in excess of 
Mr. Rickard’s estimate, later developments have not been satisfactory to the 
company, and the mine has received some notoriety from a suit entered against 
the Stratton estate to recover a portion of the purchase price on the ground of 
alleged misrepresentation at the time of sale. 


MINES OF BATTLE MOUNTAIN, EAST GROUP. 


451 


The mine was shut down for about two months in 1903, owing to a general 
strike in the Cripple Creek district. The company resumed operations for a time, 
without, however, attaining the large ore tonnage shipped before the strike, though 
the grade of ore shipped was reported as somewhat higher. At present the mine 
is worked by lessees. 

PRODUCTION AND DIVIDENDS. 

The following table exhibits the production of the mine and the dividends 
paid, the figures being taken chiefly from the original prospectus and annual reports 
of the present company. As appears from this table, which probably does not 
include all that came from -the property under Stratton’s ownership, the mine has 
produced 723,095 ounces of gold, including some silver, worth nearly $14,000,000. 
The average sales value of the unrefined gold, computed from all available data, 
has been $19.24 per ounce. With silver at 50 cents per ounce, this value would 
indicate the presence of approximately 7 ounces of silver to every 100 ounces of 
gold, or about the relative proportion of the two metals found in calaverite. 

During the fiscal year 1903-4 Stratton’s Independence produced 43,758 tons 
of ore, with a gross value of $21,695 per ton. As the total cost of production 
amounted to $24.29 per ton, the mine was operated at a loss. 

Under the leasing system in force during the year 1904-5 the total quantity 
of ore shipped by the lessees was a little less than 50,000 tons, with a gross value 
of $1,978,800. The company received approximately $509,250 in royalties and 
cleared a net profit for the year of $457,093. Since the opening of the mine to 
lessees additional dividends amounting in all to $606,250, have been declared to 
date (November, 1905), bringing the total dividends paid by the present company 
up to $4,627,730. 

Production and dividends of Stratton’s Independence mine. 


Year. 


1891-1893 

1894 . 

1895 . 

1896 . 

1897 . 

1898 . 

1899 . 

1900 . 

1901 . 

1902 . 

1903 . 


Tons of 
ore ( 2,000 
pounds to 
the ton). 

Ounces of 
gold (un¬ 
refined) .« 

Average 
ounces 
per ton. 

Gross 

value.!* 

Divi¬ 
dends. b 

2,000 

5,000 

2.50 

$ 100,000 


5,159 

26,827 

5.20 

523,859 


9,007 

61,968 

6.88 

1,208,109 


7,125 

39,544 

5.55 

794,130 


10,024 

40,946 

4.08 

751,685 


8 ,379 

24,987 

2.98 

459,576 


} d 48,048 
} d 57,534 

f c 91,421 
] 150,296 

| 120,060 
| 102,588 

l < 59,458 

} d 3. 75 
} d 2.32 

} d 1.22 

1 

3,472,189 

2,573,373 

( $970,005 

] 1,778,345 
j 788,130 

} d 96,173 

2,274,108 

1 121,250 

) d 86,257 

} d 1.06 

1,761,379 

{ 363,750 

329,706 

723,095 


13,918,408 

4,021,480 


“The mine records give output as ounces of gold, taking no separate account of silver present. The average sales 
value of this unrefined gold is $10.24 per ounce. 

b In calculation, the pound sterling is taken as equivalent to $4.85. 
c May to December. 

d For fiscal yeaf from July 1 to June 30. 
e Output curtailed by general miners’ strike. 




































452 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


UNDERGROUND DEVELOPMENT. 

The principal shaft is the Independence, situated about 500 feet north of the 
south end of the Independence claim. This is a vertical shaft about 1,430 feet in 
depth. The Xo. 2 shaft, near the north end of the property, 600 feet in depth and 
extending only to level 5, is now in disuse. The levels above 9 are 100 feet apart. 
Between level 9 and the 1,400-foot level is an intermediate level at 1,150 feet, and 
short sublevels, not directly connecting with the main shaft, at 960 and 1,150 feet 
below the collar of the shaft. 

All of the ore, with the exception of a little above level 2 and the ore bodies of the 
old Washington mine, lies north of the shaft, the productive workings thus being 
between the shaft and the Portland property. South of the shaft are a few long 
exploratory drifts and crosscuts, which on level 7 extend southward for 1,200 feet. 
The workings north of the shaft are exceedingly intricate. The drifts follow a num¬ 
ber of intersecting lodes ranging in strike from north to northwest and of various 
dips from 20° to vertical. The plans of the different levels when assembled on a sin¬ 
gle sheet form a maze of almost hopeless complexity, in which all but the drifts on 
a few of the most important and persistent lodes are obscured by the tangle of cross¬ 
ing lines. The levels above the sixth are generally more complicated in plan than 
the lower levels. 

LODE SYSTEMS. 

The most prominent lodes of the Independence mine are the Independence, 
Emerson, Bobtail, Grant, Xo. 6, and Flat veins. Their general relation to the lodes 
of the Portland mine is partly shown in PI. A' (p. 26). The Bobtail, Diamond, and 
Xo. 2 veins of the Portland, converging from the north, and the Emerson, Bobtail, 
West Bobtail, Independence, West Independence, and other veins of Stratton’s 
Independence, converging from the south, come together in a plexus of fissures near 
the boundary between the two mines. It is thus impossible to correlate with cer¬ 
tainty the veins of one mine with those of the other. On some levels the stopes on 
the Independence vein are continuous with those on the Xo. 2 vein in the Portland. 
On level 3, however, the Independence veins (PI. V) are apparently continued by 
the Diamond vein. The Grant and East veins of the Independence undoubtedly 
coalesce with the Xo. 2 zone of sheeting in the Portland. The Emerson and Bob- 
tail veins of the Independence come together near the Portland line, and it is an 
open question which should be regarded as the continuation of the Portland Bob- 
tail. All of the veins are connected by branching fissures near the line between the 
two mines, and any of these fissures may carry ore. Consequently, stopes begun on 
one vein sometimes come up on what had been regarded as an entirely distinct vein 
on the level above. The truth of the matter probably is that none of the veins 
preserve distinct individuality across the region of complex Assuring in which they 
come together. 

The rocks of the Independence mine, particularly above level 5, are cut by a 
complex network of fissures, few of which possess any features sufficiently charac¬ 
teristic to serve for their identification from level to level. This has led to some 


MINES OF BATTLE MOUNTAIN, EAST GROUP. 


453 


confusion of nomenclature, owing partly to the fact that when ore leaves one fis¬ 
sure zone and follows a branch or intersecting lode the original name of the lode is 
frequently retained in spite of the significant change in strike and dip. So far as 
observed, the intersections of the different fissure zones in the Independence mine 
are not associated with any perceptible faulting. 

An idea of the relation of the lodes in a horizontal plane may be had from fig. 
59, which is a plan of level 4. The No. 6, East, and No. 1 veins, however, have no 
development on this level. The Independence lode has a general course of N. 15° 
W., but it is far from straight. Near the Independence shaft it strikes nearly north 
and south. Farther north, however, after entering the breccia, it gradually assumes 
a nearly northwest course and then curves gently eastward until, near the Portland 
line, it again runs north and south. This curve may be seen on all the levels except 
the first. The northern part of this level follows a fissure with southwest dip, which, 
while known locally as the Independence, is probably not that lode, but a different 
one, formerly called the Black Diamond vein. The general dip of the Independence 
lode is easterly, at angles ranging from 70° to vertical. 

The Emerson lode, which lies for the most part northeast of the Independence, 
strikes N. 58° W., and dips southwest at angles ranging from about 50° near level 1 
to about 68° near level 5. The relation between the Independence and Emerson 
lodes is not clear on level 1. The Emerson turns north as it comes into the Port¬ 
land and has not been identified in that mine. The Independence or No. 2 lode is 
also very indistinct on the 350-foot Portland level (which is about 12 feet below 
level 1 of the Independence), though there is a fissure with southwest dip known as 
the Diamond vein which may be the same as the fissure called the Independence in 
the northern part of level 1 of the Independence mine. It is by no means clear, 
however, that the Diamond lode of the 350-foot Portland level is the same as the 
nearly vertical Diamond lode which proved so productive in that mine below level 5. 

On levels 2 and 3 the Independence, Emerson, and Bobtail lodes all meet close 
to the Portland line, near the No. 2 shaft of the Independence mine. On level 4 
the Emerson and Independence cross about 75 feet south of the No. 2 shaft. On 
level 5 the crossing occurs still farther south, but the indistinct portion of the 
Emerson west of the Independence is here in the granite and contains practically 
no ore. On the levels below the fifth the Emerson lode is unknown. 

The Bobtail lode lies southwest of the Emerson and strikes in general northwest. 
The two lodes thus gradually come together and both may be represented in part 
by the Bobtail in the Portland. Some of the Assuring known as the Emerson in 
the Independence mine seems, however, to turn northward in the Portland and may 
join with what are there known as the Diamond and No. 2 veins. Cross and branch 
fissures are so numerous in this vicinity and individual fissures so often nonper- 
sistent and indistinct that definite correlation is in most cases impossible. The 
Bobtail, like the Emerson, dips southwest, and at about the same angle. Its general 
relations to the Independence and Emerson are well shown in PI. Y (p. 26). Like 
the Emerson, also, the Bobtail is of no importance below level 5, though obscure 
traces of the lode may be detected in the granite on some of the lower levels. 


3 N / ty 9 N O y i $ 


454 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT, 



Fig. 59.— Map of level 4, Stratton’s Independence mine, showing vein system. 



















MINES OF BATTLE MOUNTAIN. EAST GROUP. 


455 



Fig. 60.—Map of level 8, Stratton’s Independence mine showing vein system. 


















456 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

The Grant lode lies east of the Independence and strikes about N. 23° W. It 
dips westerly at angles ranging from 55° to 70°. The Grant crosses the Bobtail and 
Emerson, and joins the Independence in the north end of the mine. It is not known 
on the levels below the fifth. The No. 6 lode lies west of the Independence lode and 
has been developed from level 5 to level 9. It strikes nearly north and south and 
is about vertical. 

In addition to the lodes hitherto mentioned there are a number of minor lodes, 
often of no great persistence. Some of these are parallel to the more important 
sheeted zones; others are plainly branch lodes. They add greatly to the com¬ 
plexity of the fissure systems and to the difficulty in following and identifying the 
principal lodes. The West Independence lode runs generally parallel with the 
Independence lode on levels 1, 2, and 3. The East Independence is a branch lode 
known only below level 8, and has by some been confused with the Emerson. The 
Bobtail has at least two branch lodes above level 3, one known as the West Bobtail 
and one as the East Bobtail. Northeast of the Emerson lode and crossing or join¬ 
ing it at various points are a number of less persistent sheeted zones known on 
different levels as the East Emerson, London, East London, Drury, East Drury, 
and East lodes. 

The Flat xnin of the Independence mine lies between levels 2 and 4, dipping 
in general about 18° W. It is best seen on level 3, which cuts it about 200 feet 
north of the shaft and immediately north of the granite-breccia contact. It con¬ 
sists essentially of two nearly parallel zones of sheeting about 8 feet apart which 
differ from the usual sheeted zones in the breccia and granite only in their unusually 
low angle of dip. The Flat vein is not very persistent and has not been identified 
with certainty on levels 2 and 4. It has been exploited for a distance of 400 feet 
in a northwest-southeast direction, and 100 to 125 feet in a northeast-southwest 
direction. It is crossed without any apparent faulting by the Independence lode 
and by a number of minor sheeted zones running generally parallel with the Inde¬ 
pendence. A similar but much less important flat vein, known as the East Flat 
vein, occurs on level 4 near the Emerson lode, the two intersecting without visible 
displacement. 

One very significant fact apparent from a study of the various levels of the 
Independence mine is the much greater abundance and more open or dispersive 
character of the Assuring in the upper levels as compared with the lower. While 
to a certain extent this change seems to be progressive from level to level, yet 
the most marked difference is between the fifth and upper levels, on the one 
hand, and the sixth and lower levels on the other (figs. 59 and 60). As will appear 
when the geological features of the mine are considered, this general fact may be 
expressed in different terms by stating that the breccia is locally much more exten¬ 
sively fissured than the granite. The diminution of the Assuring in depth is fairly 
well exhibited by a comparison of the drifts on the different levels. For while to 
some extent the fewer drifts on the lower levels merely signify a less advanced 
stage of mining development, yet they are nevertheless fairly expressive of an 
actual contrast in the relative abundance and prominence of the fissures in the 
upper and lower parts of the mine. 


MINES OF BATTLE MOUNTAIN, EAST GROUP. 


457 


GEOLOGICAL FEATURES. 

Like so many of the large mines near Victor, Stratton’s Independence is partly 
in granite and partly in breccia. In general petrographical character these rocks 
are identical with those described in the Portland mine, though, as the Independence 
workings do not extend so far into the breccia, certain facies of this rock, such as 
those in the vicinity of the Captain lodes, do not occur in the more southerly mine. 
While in the Portland mine the contact between the granite and breccia is generally 
convex toward the northeast, in the Independence it is concave (PI. V, p. 26). 
In the Portland the granite projects into the breccia as a steep promontory; in the 
Independence the breccia lies in the curved embayment on the east side of this 
jutting point of granite. The benched form of the contact surface, already described 
in the Portland, is also well exhibited in the northern part of the Independence 
embayment. (See fig. 61, p. 458.) The Independence shaft is sunk in the granite, 
the collar being very close to the granite-breccia contact as exposed at the surface. 
The drifts running north from the shaft at successivelv lower levels cut the contact 
at increasing distances from the shaft (fig. 62), the successive increments of dis¬ 
tance being such as to show that this portion of the contact has a general dip of at 
least 60° N. or NE. Farther north, however, the dip becomes considerably less than 
this above level 5 and considerably more below it. There is thus in the north¬ 
western part of the mine, adjoining the Strong and Portland mines, a notable 
bench-like flattening of the granitic surface against which the breccia rests (PI. V, 
p. 26 ; fig. 62, p. 459). As a consequence of this, the productive northern portions of 
the levels above the fifth are chiefly in breccia, while below level 5, the workings are 
chiefly in granite. This fact may be exhibited with greater clearness by noting 
the relation of the Independence lode to the country rocks on different levels. On 
levels 1, 2, and 3 the lode, in granite near the shaft, soon passes into breccia and 
continues in this rock past the Portland line. On level 4, the Independence lode 
passes into breccia about 250 feet north of the shaft, and thence northward remains 
wholly in this rock. The granite, however, on this level appears again in the 
Strong drift, about 325 feet west of the Independence vein (PL V, p. 26), showing 
that the dip of the contact is bringing the latter nearer the vein. On level 5 the 
lode enters the breccia about 300 feet north of the shaft; but about 675 feet north 
of the shaft, near the crossing of the Emerson lode, the granite reappears and 
continues to form the west wall of the Independence lode into the Portland ground. 
Below level 5, there is practically no breccia west of the Independence lode, the 
latter being either wholly in granite or following in a general way the steep granite- 
breccia contact (fig. 62). This statement, however, requires some qualification 
with reference to the 1,400-foot level. The granite-breccia contact near the north 
end of this level is indistinct, and the narrow fissure, supposed to be the Independence 
vein, apparently enters a granitic phase of the breccia about 100 feet south of the 
Portland line. Whether or not this is merely a level irregularity in the contact 
could not be determined. 

The granite-breccia contact is hardly so well exposed in the Independence 
workings as in the Portland. In general it is fairly distinct on the upper levels, 
the granite as a rule not showing much brecciation in its vicinity. In detail it is 


458 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

exceedingly irregular, diversified with minor salients and reentrants. The breccia 
near the contact is sometimes, as on the 1,400-foot level, so full of granite fragments, 
some of them of large size, that it is difficult to determine in a small exposure 
whether the rock seen is breccia or massive granite. 

Both granite and breccia are cut by phonolite in the form of dikes, sills, and 
irregular masses. In general the Independence lode, as known in the granite, 
follows a phonolite (strictly latite-phonolite) dike, but the dike, as pointed out by 
Penrose,® is much more irregular in its course than the lode and the two are not 



Fig. 61.—General north-south section through Stratton’s Independence mine, showing stopes in Independence vein. 


always together. The extensive developments in the breccia since Penrose’s visit 
show that in that rock the relation between dike and lode is less close than in the 
granite. The dike becomes more irregular as it enters the breccia, branches, and 
frequently sends off intrusions along the contact between the breccia and the 
granite. While several of the lodes in the breccia follow phonolite dikes for varying 
distances, it can not be said that any single lode and dike are continuously associated 
throughout their known horizontal and vertical extent. For example, the West 
Independence lode on level 2, is generally associated with a phonolite dike. On 


a Sixteenth Ann. Rept. TJ. S. Geol. Survey, pt. 2, 1895, p. 201, pi. 14. 






































































MINES OF BATTLE MOUNTAIN, EAST GROUP, 


459 



Pxg. 62._Section through Stratton’s Independence mine, showing the relation of the veins to the granite-breccia ontact. 


















460 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

level 3 what appears to be the same dike lies between the Independence and the West 
Independence lodes in the southern part of the mine, but turns southeastward 
across the Independence lode, crosses the Flat vein in the large stope just above 
level 3, known as the Little Bull Pen, and meets the granite-breccia contact about 
150 feet east of the Independence lode. Here it apparently joins with an irregular 
dike-like intrusion which follows the contact and may be seen in the main Inde¬ 
pendence and Bobtail drifts where they pass from breccia into granite. On level 4, 
the same Independence dike is crossed by the Independence lode about 75 feet south 
of the Independence-Bobtail intersection and is cut by the Bobtail northwest of 
that intersection. Thus on this level it exhibits no significant connection with 
either lode, though it contained a comparatively short ore shoot which branched 
in a southeast direction from the main Independence pay shoot. On level 5, a 
phonolite dike, apparently the same Independence dike, lies in the granite west of 
the Independence lode in the northern part of the mine and crosses to the west side 
of the No. 6 lode near the Portland line. The No. 1, Bobtail, and East Bobtail 
lodes accompany phonolite dikes for part of their courses on this level, the dike along 
the Bobtail fissure zone connecting with an irregular phonolite intrusion at the 
granite-breccia contact. On level 6, the Independence phonolite dike is followed 
by the main drift north to the breccia, in which, as usual, it becomes irregular. 
A little phonolite, possibly a part of this dike, occurs along the Independence lode 
near the Portland line. On level 7, the Independence phonolite dike has been 
followed northward from the shaft for a distance of 450 feet, to the breccia, and 
south of the shaft for about 1,050 feet. At the south end of the mine the dike 
terminates abruptly against a close cross fissure. There is no evidence of move¬ 
ment along this fissure subsequent to the plionolitic intrusion. The original 
dike fissure apparently ended at this point. On level 8, the Independence dike is 
cut near the shaft and followed northward for 350 feet in the main drift. Here it 
apparently branches, one branch turning northwestward and the other continuing 
north and probably connecting with some phonolite exposed at the south face 
of the East Independence lode, at the granite-breccia contact. On level 9, the dike 
runs generally north from the shaft for about 300 feet and then turns northwest, 
away from the Independence lode. On the 1,150-foot level the Independence 
dike accompanies the Independence lode for a distance of 700 feet north of the shaft 
to the granite-breccia contact. Be 3 mnd this point it v r as not seen. On the 1,400- 
foot level it runs north for 300 feet from the shaft, and then divides, one branch 
turning northwestward, as on levels 8 and 9, and the other continuing north to the 
contact. A west crosscut on this level exposes other phonolite dikes in the granite 
which have no apparent connection with lodes. A long southeast drift or crosscut 
on the same level, approximately along the granite-breccia contact, shows some 
very irregular dikes of phonolite and a number of sill-like intrusions of the same 
rock, dipping gently eastward and cutting both granite and breccia near the contact. 

The main phonolite and “ basalt ” dikes of the Strong mine are exposed in several 
drifts near the Independence-Strong line in the extreme western portions of several 
of the Independence levels, but as these dikes are fully described in connection 
with the Strong mine they need not be further considered at this place. With the 
exception of the Strong dike and some small decomposed basic dikes in the western 


MINES OF BATTLE MOUNTAIN, EAST GROUP. 


461 


part of the mine that are probably part of the same dike zone known in the Strong 
mine, “basalt” dikes are absent in the Independence mine. 

The northeastern part of the Independence property, particularly the ground 
under the northern part of tract A of the Wilson Creek placer location and under 
the northern half of the Wonderland claim, has not been thoroughly explored. 
Such long crosscuts, however, as have been run out into the breccia in this territory, 
on the third, fourth, and 1,400-foot levels have not been particularly encouraging. 
On level 4 (PI. V, p. 26) a long northeasterly crosscut which crosses and recrosses 
the Portland line cuts the same latite-phonolite noted in the Portland mine east 
of the No. 2 lode. The contact between this rock and the breccia which is locally 
banded, is not entirely definite, though it can in some places be determined within 
the range of a foot in distance. The massive rock is not particularly shattered 
near the contact and its contrast in texture and composition with the breccia a 
foot or so away is suggestive of intrusion into the latter. 

PAY SHOOTS AND LODE STRUCTURE. 

Bv far the greater part of the ore from Stratton’s Independence mine has come 
from that part of the breccia filling the granitic embayment and lying above the 
bench-like flattening of the contact above level 5. Good ore occurs in the granite 
in the Independence lode above level 3 in the old Washington workings near the 
surface, and in the No. 6 vein, but the amount of ore hitherto extracted from this 
rock is small indeed compared with the great tonnage obtained from the breccia. 
Between the fifth and 1,050-foot levels a large amount of ore has been mined from 
the part of the Independence lode that follows the general course of the granite- 
breccia contact. 

The ore bodies occur as pay shoots in lodes, such irregular ore masses in 
granite as occur in the Ajax and Elkton (Thompson) mines having here no exempli¬ 
fication. These pay shoots in some cases attain considerable width, the stopes 
along the Bobtail on level 4 being in places 50 or 60 feet wide. Such wide ore 
bodies are usually associated with a corresponding widening of the zone of generally 
parallel sheeting constituting the lode, or with the convergence or intersection of 
two or more definite lodes. 

The main pay shoot of the Independence lode begins at the surface, about 250 
feet south of the granite-breccia contact, and extends northward practically to the 
Portland line. Its southern limit pitches north at an angle with the horizon 
which may be generalized at about 52°, a somewhat lower angle than that of the 
granite-breccia contact. Below level 3 the ore rarely extends from the breccia 
into the granite, and then only for short distances. On levels 1, 2, and 3 the ore 
in the granite occurred in a sheeted zone apparently of the usual type found in 
this rock, though the details of the occurrence of this ore could not be studied in 
1904. Below level 3 the Independence lode between the shaft and the granite- 
breccia contact is usually a rather indistinct, narrow zone of Assuring in the granite 
or in the Independence phonolite dike, and contains practically no ore. At the 
contact the lode usually becomes rather irregular, apparently splitting into several 
branching fissures, and the ore generally begins abruptly as the breccia is entered 
and continues almost continuously to the Portland line. The ore occurs in a 
13001—No. 54—06-31 



462 GEOLOGY AKD GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


mineralized sheeted zone in breccia, granite, however, forming a portion of the foot- 
wall from level 5 down. Owing to the northerly dip of the contact, the portion 
of this great pay shoot lying in the Independence ground becomes shorter on 
successive lower levels. Below the 950-foot level, moreover, the ore becomes 
narrower, and on the 1,150-foot level all that is known of the Independence lode is a 
single narrow fissure containing a little fluorite and pyrite, but no workable ore. 
On the 1,400-foot level the lode is even less distinct, and it is doubtful whether 
it can be recognized with any certainty. In general, the Independence lode 
exhibits the same structural characteristics as its northern continuation, the Xo. 2 
vein of the Portland, which has already been described. It will be unnecessary, 
therefore, to do more than note a few special features. On level 7 the pay shoot 
extends for a short distance into the granite, south of the contact, as a mineralized 
sheeted zone about 4 feet wide, consisting of three principal parallel fissures. These 
little fissures are partly filled with fluorite, quartz, pyrite, and calaverite. 

On level 6 the first ore in the Independence lode, as one goes north, occurs 
in an irregular expansion of the Independence phonolite dike at the granite-breccia 
contact. Thence northward it occurs partly in breccia and partly in phonolite, 
close to the granite. Where the phonolite is sufficiently mineralized to constitute 
ore, the rock has a porous texture, being full of little cavities containing nests of 
pyrite, fluorite, and calaverite. The same minerals occur also in the narrow 
crevices of the sheeted zone and" in less regular minute cracks traversing the rock. 
Where the lode passes through breccia containing granitic fragments, the latter 
usually show the same porous texture and the same character of mineralization 
as occur along the Diamond lode in the Portland and in the granitic ore bodies of 
the Ajax and Elkton mines. On level 5 the Independence pay shoot attains its 
greatest width at the crossing of the Emerson lode. On level 4 are several local 
expansions of the ore to unusual width. The first of these is just north of the 
contact, where the main lode is crossed at small angles by some fissures running 
approximately northwest and southeast, or parallel with the Bobtail lode. The 
ore here, which is under the Flat vein, attains a width of about 40 feet. This ore 
is all in breccia, the value, as usual, being concentrated in the actual fissures. 
Another wide body of ore occurs at the crossing of the Bobtail, which on this level 
comprises a large number of parallel fissures forming a sheeted zone about 50 feet 
in width. A smaller though important widening of the ore occurs at the crossing 
of the Emerson, and, finally, at the Portland line, the convergence of the Independ¬ 
ence, Grant, and East lodes determines a large ore body which has been worked 
in the great Independence stope on the Xo. 2 vein in the Portland. On level 3 
a body of ore fully 50 feet in width was stoped in the breccia just north of the 
contact, at the intersection of the Independence lode with the Flat vein and with 
the northwest-southeast fissures already noted. 

The Emerson and Bobtail are essentially sheeted zones in breccia, and their 
pay shoots are generally rather narrow. At points of intersection with other 
fissures, however, or where other sheeted zones of generally parallel strike but 
slightly different dips approach so near as to constitute locally a single fissure zone, 
the ore bodies may expand to unusual dimensions. This is particularly striking 
along the Bobtail lode on level 4, where several fissures of nearly parallel strike, 


MINES OF BATTLE MOUNTAIN, EAST GROUP. 


463 


which are distinct on level 3, join to form a single ore body, which for a length of 
over 200 feet has a width of 40 or 50 feet. The Emerson pay shoot attains its 
maximum length (about 600 feet) on level 5. A short distance below this level 
the lode, if it persists, enters the granite, and within this rock, so far as known, it 
carries no ore. On the northwest the pay shoot ends near the Portland line. On 
the southeast the pay shoot, as seen on level 5, continues for about 150 feet south¬ 
east of the crossing of the Drury lode. The Emerson sheeted zone, however, 
continues in the breccia beyond this point, but has not been followed to the granite- 
breccia contact. 

The Bobtail pay shoot reaches its greatest length (about 1,000 feet) just above 
level 2. This diminishes to about 450 feet on level 5. A short distance below 
this level the Bobtail, like the Emerson, meets the granite-breccia contact and 
the economic importance of the lode vanishes. On the northwest the pay shoot 
reaches the, Portland line only near level 2. On the southeast the ore extends 
up to the granite-breccia contact on level 3, but on all- other levels ends well within 
the breccia, though this fissure zone apparently continues to the contact and 
probably into the granite. 

The Grant, Drury, East, and London lodes are usually narrow sheeted zones 
in the breccia and are not known below level 5. They contain several important 
pay shoots, which, however, are not so persistent in depth and length as those of 
the Independence, Emerson, and Bobtail. The occurrence of their ore bodies 
could not be well studied at the time of visit, but they appear to be of the usual 
structural type—narrow zones of close sheeting, with the value chiefly in the form 
of calaverite in the fissures. 

With the exception of the upper 300 feet of the Independence lode and the 
contested portion of the Strong lode, the only important lode known in the granite 
of the Independence mine is the No. 6 lode. This has shown a fairly continuous body 
of ore from the granite-breccia contact above level 5 (fig. 62, p. 459) to level 6 
and isolated ore bodies between levels 6 and 9. The lode is a narrow sheeted 
zone in granite, in some places following a phonolite dike. The granite between 
the fissures is altered to a porous mass consisting chiefly of secondary feldspar, 
with nests of pyrite and calaverite partly filling the irregular cavities. The best 
ore occurs in a rather soft decomposed streak, usually from 3 to 8 inches in width, 
and is worth about $50 per ton. 

One of the most interesting ore bodies in the mine was that stoped from the 
Flat vein above and below level 3. This stope has a length from southeast to 
northwest of about 400 feet, and an extreme width of about 200 feet. The ore had 
an average thickness of 6 or 7 feet and dipped northwesterly at about 18°. It lay 
generally in the breccia, being bounded on the southwest by the granite, and passing 
somewhat irre°;ularlv into barren breccia in other directions. The ore occurred 
in a sheeted zone, which in some portions of the stope is divided into two zones 
by a slab of country rock. These zones of sheeting are not merely coextensive 
with the ore, but persist bejmnd the margin of the ore body into the granite and 
into the breccia. The Flat vein is crossed by the Independence lode and phonolite 
dike, and by a number of other fissures of general northwest strike. The ore was 
continuous with that of the Independence lode and extended for varying .distances. 


464 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

above and below the Flat vein into some of the other nearly vertical fissures. Still 
other fissures contain ore only at their intersection with the Flat vein. The flat 
ore body may be regarded as a special case of the local expansion or coalescence 
of ore bodies at the intersections of lodes. The mine affords several examples of 
such ore bodies at the intersections of nearly vertical fissure zones. The intersec¬ 
tions of such lodes with the Flat vein appear to have supplied unusual facilities 
for ore deposition, some of the richest ore having been stoped from this body. 
The value, as usual, was in the small fissures of the sheeted zones, the calaverite 
being accompanied by fluorite and partly oxidized. 

VALUE AND CHARACTER OF THE ORE. 

The average value of the ore produced by Stratton’s Independence mine has 
varied from a maximum of $132 a ton in 1895 to $20 in 1903. During March, 
1904, 4,650 tons of ore were shipped, which averaged about $30 a ton. Some of 
the ore formerly stoped from the Flat vein is said to have been wonderfully rich, 
though no actual figures for the value of carload lots have been obtained. A 
small sample bag of ore stolen from this vein and afterwards recovered was found 
to contain $80 in gold. 

There were comparatively few places where the actual occurrence of ore could 
be well studied in the Independence mine at the time of visit. The richest ore, 
on the whole, occurred in the Flat vein as calaverite associated with fluorite in 
very narrow fractures in the breccia, and probably to some extent in the porous 
metasomatically altered granitic fragments traversed by these fissures. This ore 
was partly oxidized. 

The ore of the Independence vein is of the same general character as that in 
the No. 2 vein of the Portland. Owing to the abundance of granitic fragments 
in the breccia along the course of this vein, the ore partakes somewhat of the char¬ 
acter of ore found in the massive granite. The granitic fragments alongside and 
between the fissures are altered to spongy aggregates consisting chiefly of secondary 
orthoclase or valencianite, with fluorite and considerable pyrite in small crystals. 
Calaverite and perhaps sylvanite occur in the fissures of the sheeted zone, usually 
with quartz and fluorite, and in the metasomatically altered granitic breccia as 
particles usually too small to be detected with the naked eye. 

The ore of the No. 6 vein is similar in mineralogical character to the Diamond 
ore in the Portland mine, though the metasomatic alteration has been much less 
extensive in the Independence mine. 

Some very rich ore, consisting of little irregular stringers of nearly solid cala¬ 
verite in dark sheeted breccia, has come from the Emerson vein near level 4. The 
calaverite is intimately associated with P3 T rite, molybdenite, and a little quartz 
and fluorite. Pyrite is also finely disseminated through the breccia near the vein, 
but so far as known is not auriferous. 

* In many places ore occurs in plionolite dikes, nearly always as calaverite in 
very narrow fissures associated with fluorite and quartz as gangue. 

Galena is rarely visible in the Independence ore, but is said to have occurred 
in considerable abundance in the Bobtail vein above level 2. It also occurs spar¬ 
ingly in the Emerson vein just above level 7. 


MINES OF BATTLE MOUNTAIN, EAST GROUP. 


465 


UNDERGROUND WATER. 

The first water encountered in the Independence mine was 275 feet below 
the collar of the shaft, or 9,569 feet above sea level. In January, 1895, the shaft, 
then 300 feet deep, could be kept free of water by raising about 25 gallons a minute. 
At the time of sale in 1899 the mine, then 900 feet deep, made about 350 gallons 
of water a minute. In January, according to Mr. V. G. Hills,® the quantity of 
water pumped was 300 gallons a minute. This, however, was being considerably 
augmented by development work on the 1,400-foot level, and in July of the same 
year the flow had increased to 450 gallons. The hulk of this water issues from 
fissures in the granite in the northern part of the level. The level at which the 
water would stand if pumping were abandoned is estimated by Hills at 8,940 
feet above sea level, or about 913 feet below the collar of the shaft. On April 17, 
the quantity of water raised by the pumps had increased to 560 gallons a minute, 
the increase being due to additional development work on the 1,400-foot level. 


a Fourth Ann. Rept. Portland Gold Mining Company, 190'?, p. 91. 






/ 


4 


CHAPTER VIII. 


-MINES OF BATTLE MOUNTAIN (WEST GROUP) AND 
OUTLYING PROSPECTS. 


STRONG MINE. 


INTRODUCTION. 

The Strong mine, situated on the southern slope of Battle Mountain, near the 
northern limits of the town of Victor, is owned by the Strong Gold Mining Com¬ 
pany, of Colorado Springs, incorporated in 1892 with a capital of $500,000. It lies 
between Stratton’s Independence mine on the east and the Dillon mine on the west. 
On the north it joins the Portland property. The Strong workings were originally 
confined to the Strong claim, running about N. 6° W. By compromise with the 
Portland company, however, 250 feet from the north end of the Strong claim were 
exchanged for a triangular area extending southward from the Portland property 
between the Strong claim and the Maggie claim of Stratton’s Independence mine 
and tapering to a point about 600 feet south of the northeast corner of the original 
Strong claim. 

PRODUCTION. 


Statistics of the gross production of the Strong mine are not obtainable, but 
for a comparatively small mine it has been a remarkably regular and profitable 
producer. The dividends paid are as follows: 


1892-189G 

1897 . 

1898 . 

1899 . 

190C. 


Dividends paid by Strong mine. 


$555, 000 

1901.. 

145,000 

1902.. 

300,000 

1903.. 

300,000 


300,000 



$300, 000 
375, 000 
200,000 


2, 475, 000 


UNDERGROUND DEVELOPMENT. 

Access to the Strong workings is through the vertical Strong shaft, 904 feet in 
depth and situated about 340 feet from the south end of the claim. There are 
nine levels, approximately 100 feet apart. These are of generally linear plan and 
run nearly north and south. The principal development has been north of the 
shaft. The northern portions of levels 2, 3, 4, and 5 were not accessible at the 
time of visit, being partly caved in and partly bulkheaded. 

LODE SYSTEMS. 

There is but one important lode in the Strong mine—a nearly north-south zone 
of sheeting, which usually dips to the east at angles ranging from 80° to 90°. The 
general dip is about 84°. As will presently be shown, this lode is closely related to 
two nearly north-south dikes, one of phonolite and one of basalt. 

466 


4 












BATTLE MOUNTAIN MINES, WEST GROUP, AND OUTLYING PROSPECTS. 467 


GEOLOGICAL FEATURES. 

The general country rock of the mine is the conspicuously porphyritic Pikes 
Peak granite prevalent in this part of the district. Here, as elsewhere, this granite 
often exhibits a distinct gneissoidal structure. The northern portions of levels 1, 2, 
and 3, and perhaps also of levels 4 and 5, extend into the breccia, the contact 
between the granite and the breccia being irregular, but distinct. On level 1 the 
breccia is first seen in the main drift about 425 feet north of the shaft. The con¬ 
tact, which is followed for about 500 feet by the drift, runs in a general north- 
northwest direction for about 300 feet and then turns nearly due north toward 
the Burns shaft of the Portland mine. On level 3 the contact crosses the main 
drift about 600 feet north of the shaft, and has been drifted on for about 500 feet 
northward from this point. Its general course is similar to that on level 1, and its 
dip, as shown by the relative positions of these two levels, is easterly, ranging from 
65° on the south to 85° on the north. The breccia seen in the Strong mine presents 
no unusual character and is similar to that already described in the southwestern 
part of the Portland mine. 

There are two important phonolite dikes in the Strong mine. The larger and 
better known of these, while somewhat irregular in trend, has in the main a north- 
south course. It has been identified on all of the levels and extends through the 
Strong claim, entering near the middle of the south end line and passing out near 
the northeast corner. It thus cuts both granite and breccia. Its general dip is 
that of the Strong lode, the two being sometimes coincident for several hundred 
feet. When not coincident the phonolite dike usually lies a tew feet east of the 
lode, though in one place, on level 6, it lies immediately west of the ore. The average 
width of the dike is about 7 feet. It is composed of the altered greenish-gray 
aphanitic phonolite, with platy parting parallel with the walls, that constitutes the 
common dike facies in the Cripple Creek mines. 

The second phonolite dike, known as the “ cross dike,” derives its name from the 
fact that its course crosses that of the first dike. It is apparently more irregular 
and less persistent than the main dike, its course, as observed on different levels, 
varying from west-northwest to north-northwest. The dip is in general to the 
southwest. On level 1 the cross dike is exposed in breccia in the right-hand branch 
of the main north drift, about 800 feet north of the shaft. Its course as exposed 
for a length of 70 feet is far from straight, but seems to be in general about west- 
northwest. It was not noted in the left-hand branch of the drift and may not 
cross the granite-breccia contact (PI. V, p. 26). On level 3 the dike is in granite 
and intersects the main phonolite dike 575 feet north of the shaft. There is no 
evidence at the crossing that one dike is older than the other, and they were probably 
intruded simultaneously. The dip of this portion of the cross dike, as indicated by 
its relative positions on levels 1 and 3, is southwest at an angle of about 40°. On 
level 4 the dike could not be seen, but on level 5 it is encountered about 600 feet 
north of the shaft and followed for some distance by the main drift. Its course 
here is roughly north-northwest. It is not altogether certain that this is the same 
cross dike known on the upper levels. If it is, it indicates not only a pronounced 


468 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

change in the strike of the dike, but a local reversal of dip between levels 3 and 5 
from 40° SW. to about 80° SE. Such irregularity, however, is in full accord with the 
observed behavior of other phonolite dikes in the granite, as may be seen, for 
example, in the Gold Coin mine. 

Below level 5 the cross dike, while retaining its north-northwest strike, resumes 
its southwesterly dip. It is apparently not exposed on levels 6 and 7, but is well 
shown on level 8, 470 feet north of the shaft, and on level 9, 450 feet north of the 
shaft. Its dip in the lower part of the mine thus appears to be about 75° SW. 

In addition to the phonolite dikes there is in the Strong mine a basic dike which 
is important from its relations to the ore bodies. This dike has the same general 
course as the main phonolite dike, lying sometimes on one side and sometimes 
on the other side of the latter. The “basalt” dike cuts the phonolite dike and 
is therefore younger. It is probably not perfectly continuous, but pinches out 
locally to appear again in another parallel fissure a few feet to the east or west. 
The width of the dike varies from a fraction of an inch up to 3 feet. The usual 
width is about 18 inches. The rock is generally rather soft and decomposed, 
exhibiting the fine platy parting and calcitic veining parallel with the walls which 
is characteristic of the basic dikes in this district. The only trace of the dike 
seen on level 1, is a little streak of decomposed “basalt” lying between the ore 
and the main phonolite dike, about 100 feet south of the shaft. On level 3, how¬ 
ever, the “basalt ” dike is well developed, lying from 25 to 40 feet east of the shaft. 
It has been drifted on here for about 200 feet, but is not exposed in the northern 
part of the level. On level 5 the dike lies 40 feet east of the shaft and is here coin¬ 
cident with the Strong lode. The ore leaves the dike, however, about 125 feet 
north of the shaft, the dike lying in the east wall. About 250 feet north of the 
shaft the dike is offset about 15 feet at a cross fissure. While this cross fissure 
may possibly be a fault, of later age than the dike, close examination rather indi¬ 
cates that this offset of the north-south fissure existed before the intrusion of the 
basalt. The general relations of the “ basalt ” dike to the phonolite dikes and to the 
Strong lode on level 5 are shown in PI. Y (p. 26). On level 6 the “basalt ” is first 
seen about 250 feet north of the shaft and is thence followed northward by the 
main drift. About 450 feet north of the shaft the main phonolite dike appears, 
and from here to the north end of the level both dikes run together, the “basalt’ 
cutting across from one side to the other of the phonolite. A similar relation 
between the two dikes exists also on level 7. On level 8 the dike is drifted on 
about 50 feet east of the shaft, and appears again in the northern part of the level, 
where it accompanies the phonolite dike. On level 9 also the basic dike lies 40 
or 50 feet east of the shaft, but about 100 feet north of the shaft it turns nearly 
north-northwest, running about 100 feet southwest of and nearly parallel with 
the phonolite cross dike. This is probably an offshoot from the main dike along 
some branch fissure; in which case further development on and below level 9 will 
discover another “basalt’’-filled fissure more nearly in the general north-south 
line of the dike as known on the upper levels. 


BATTLE MOUNTAIN MINES, WEST GROUP, AND OUTLYING PROSPECTS. 469 
FORM AND STRUCTURE OF THE ORE BODIES. 

All of the Strong ore occurs in the form of lodes or veins and most of it within 
two pay shoots in the main Strong lode. One of these pay shoots near the shaft 
is known as the south shoot and is separated from the north shoot on all levels 
by a greater or less interval of barren ground. 

The south pay shoot has been stoped almost from the surface to level 9. It 
attains its maximum length (about 550 feet) on level 3. On all levels above the 
eighth this ore body extends both north and south of the shaft, lying chiefly, 
however, on the north side. Practically no ore has been found south of the shaft 
on levels S and 9. As no stope maps are kept, the shape of this pay shoot can only 
be surmised from what is visible in the drifts. It appears to be on the whole nearly 
vertical, tapering irregularly almost to a point on level 9. It is essentially a min¬ 
eralized sheeted zone in granite. On level 1, however, the main phonolite dike 
forms the east wall of the lode. On level 5 the lode and the basic dike are coin¬ 
cident for nearly 300 feet. The ore, however, occurs entirely within the granite, 
alongside the dike, the latter being waste. On levels 6, 7, and 8 neither phonolite 
nor “ basalt ” occurs with the ore. 

As no work was being done on the south pay shoot at the time of visit the mode 
of occurrence of this ore could not be satisfactorily studied. The pay shoot is 
said to have been rather narrow, but richer on the whole than the north shoot. 
There were no definite walls to the ore, which passed through low-grade ore into 
the granitic country rock. The lode appears to have been intermediate in character 
between those like the Dorothy of the Gold Coin mine, where the value is practically 
confined to the actual fissures, and those like the Diamond of the Portland mine, 
where the metasomatically altered granite between the fissures is also ore. 

The north pay shoot apparently first becomes of importance near level 4, though 
a small chimney-like body of ore is said to have extended from the south end of 
the pay shoot up to level 2. On levels 5 and 6 the north pay shoot is respectively 
200 and 400 feet long and is typically developed. The main phonolite dike, about 
7 feet wide, is here closely followed by the basic dike. The latter lies usually on 
the west side of the phonolite, sometimes in contact, but frequently separated by 
a few feet of granite. At one place on level 6 the “basalt” cuts across to the east 
side of the phonolite, follows the east contact for about 125 feet, and then again 
crosses the phonolite to the west side. The ore closely follows the “basalt,” which, 
however, is itself of no value. The phonolite dike also appears to have influenced 
in some way the ore deposition, for it is noticeable that the ore very rarely accom¬ 
panies the basic dike when it diverges for any considerable distance from the phono¬ 
lite. The ore occurs almost wholly in the granite. Where the two dikes are in 
contact, side by side, the “basalt” constitutes a definite wall, limiting on one side 
ore which on the other sides grades indefinitely into the granite. Where the two 
dikes are not in contact, the intervening slab of granite is usually mineralized and 
constitutes ore. Such ore has two definite walls—the phonolite dike on the one 
side and the basic dike on the other. The latter dike at such places thus has ore 
on both sides. The cases where the phonolite is sufficiently mineralized to be ore 


470 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


are usually at those points where the “basalt” cuts across the phonolite. On 
level 9, at the time of visit, the north ore shoot had been found and had been drifted 
on for about 200 feet. Stoping had not begun, however, on this level. 

The mineralization of the granite in the north pay shoot is not related to such 
distinct parallel sheeting as is observable in the south pay shoot. The ore-deposit¬ 
ing solutions apparently worked outward from the narrow channels furnished 
by the platy partings and contact planes of the dikes and took advantage of such 
small irregular cracks and joints as existed in the granite. The granitic ore is 
usually rather spongy in texture, closely resembling that from the Diamond lode 
in the Portland mine or from the large southwest stope in the Ajax mine. Con¬ 
trary to the practice in most of the mines in the district, very little assaying is 
done in the Strong mine, the ore usually being readily distinguished from the 
county granite by its color and greater porosity. 

CHARACTER OF ORE. 

The ore of the Strong mine is almost entirely metasomatically altered granite. 
Rounded residual kernels of the original pink microcline of the granite remain, but 
the quartz and biotite have been completely changed to a porous aggregate of 
adularia, quartz, fluorite, pyrite, and calaverite. The adularia is easily distinguish¬ 
able under the microscope from the original microcline by its greater clearness and 
frequent sharply automorphic outline. The secondary leklspar is often optically 
continuous with an older individual of microcline, the two being separated by a sharp 
sinuous line. The tiny crystals of adularia are rarely optically homogeneous, but 
appear to be built up of wedge-like or sector-shaped portions that extinguish at 
slightly different angles, and produce an optical effect similar to that often observed 
in thin sections of vein quartz and illustrated in the quartz of this same ore. The 
quartz in the Strong ore occurs in allotriomorphic grams cn^stallized with the 
secondary feldspar and as a crystalline film lining the little irregular vugs of the 
porous altered granite. Fluorite is not very abundant in the ore; it occurs usually 
as little implanted crystals in the vugs or in minute fissures in the original microcline. 
Pyrite occurs abundantly disseminated in minute crystals through the secondary 
minerals of the ore, and these crystals are sometimes gathered into little nests or 
bunches. Calaverite seems to closely accompany the pyrite and occurs in such 
minute particles that it can rarely be detected or distinguished from the pyrite 
even with a hand lens. No oxidized ore is now worked in the Strong mine. 

UNDERGROUND WATER. 

According to an estimate made by Mr. V. G. Hills,° in July, 1903, the water level 
in the Strong mine, were pumping discontinued, would stand at 8,984 feet above 
sea level, or 771.99 feet below the collar of the shaft. At that time, however, it 
was kept down by pumping to 8,872 feet, or 883.99 feet below the collar. The 
water was held at this point and level 9 kept open by pumping about 500 gallons 
a minute. In April, 1904, this amount had decreased to 330 gallons. The greater 
part of this water comes from the northern part of level 9. Xo data exist 


a Ninth Ann. Kept. Portland Gold Mining Company, 1903, p. 87 





BATTLE MOUNTAIN MINES, WEST GROUP, AND OUTLYING PROSPECTS. 471 

for determining the original water level of the mine. The height to which the water 
rises when pumping is stopped has slowly decreased since the shaft was sunk to its 
present depth. 

GRANITE MINE. 

INTRODUCTION. 

The Granite mine, owned by the Granite Gold Mining Company, of Denver, 
capital $1,000,000, is situated on the northern edge of Victor, between the Portland 
and Monument mines on the east and the Ajax, Dead Pine, and Gold Coin mines on 
the west. The workings are embraced within the generally north-south Granite 
claim. The mine is operated under the leasing system. 

PRODUCTION. 

The Granite mine is credited with a gross production of 8400,000 prior to Janu¬ 
ary 1, 1900. We have been unable to secure any later statistics. 

UNDERGROUND DEVELOPMENT. 

The main shaft, 1,000 feet in depth, is situated on the eastern edge of the claim, 
250 feet from the northeast corner. The first level below the collar of the shaft is 
the so-called level 5, 445 feet below the surface. Level 6 is 150 feet below level 5. 
Then follow levels 7, 8, and 9, 100 feet apart, and finally level 10, 80 feet below 
level 9. The workings lie mainly south of the shaft, comprising on most levels a 
main north-south drift, reached by a westerly crosscut from the shaft, and various 
spur and parallel drifts with their connecting crosscuts. Level 6 is the most exten¬ 
sive, connecting on the west with the Dead Pine mine and on the east with the 
Portlaifd mine. A drift on this level also passes under the Monument shaft. About 
380 feet from the south end of the claim is the South shaft, about 200 feet deep, 
connecting with three short levels. These were not visited. 

LODE SYSTEMS. 

In the Granite, as in the Monument and Dillon mines, two prevalent systems 
of fissures are recognizable, one set striking nearly north, while the other set strikes 
nearly northwest. The most prominent of the nearly north-south fissure zones is 
the Granite lode, striking N. 8° E. This lode varies in dip on the different levels, 
but on the whole is nearly vertical. West of the Granite, at a distance near the 
middle of the claim of about 100 feet, is the West lode, striking in general due north 
and also approximately vertical. About 50 feet east of the Granite is the East 
lode, striking N. 5° E. This fissure zone has been drifted only on level 9, but, like 
the others, seems to be about vertical. On level 10 a fourth fissure zone, striking 
north, has been followed between the Granite and West lodes. 

The most prominent northwest fissure zone is the Bobtail—clearly the same 
lode as the Bobtail of the Portland mine. It dips about 60° SW. On level 5 the 
Bobtail crosses at the shaft. On level G it lies about 90 feet and on level 7 about 130 
feet southwest of the shaft. On levels 8, 9, and 10 the Bobtail is supposed by those 


472 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

working the mine to cross the main drift close to the granite-breccia contact, about 
150 feet southwest of the shaft. No work, however, has been done on the supposed 
Bobtail on these levels, and it is probable that the Bobtail lode, elsewhere unusually 
regular and persistent, instead of turning practically vertical, maintains its charac¬ 
teristic southwest dip and passes into the granite, as in the Portland mine. If so, 
it may be represented on level 10 by a strong fissure, dipping southwest, which is 
cut in the main drift 250 feet south of the shaft crosscut. 

Southwest of the Bobtail is the Cross lode, striking northwest, and cut by the 
main drift on level 5 about 300 feet south of the shaft. If the fissure zones known 
on the different levels as the Cross vein are really all portions of the same lode, 
that lode exhibits rather notable changes in dip. Between levels 5 and 6 it is vertical 
Between levels 6 and 7 it dips about 75° NE., while between levels 9 and 10 the dip 
is about 65° SW. As there are no continuous stopes on the Cross lode below level 
6 it is not improbable that different fissures, having generally a common northwest 
strike, have been erroneously identified as the Cross lode. It frequently occurs in 
this part of the district that a narrow sheeted zone in granite, after being followed 
for a few hundred feet, becomes very indistinct, while a neighboring fissure zone of 
approximately parallel strike becomes correspondingly more regular and conspic¬ 
uous. On level 5 the Cross vein apparently has no continuation northwest of the 
Granite lode. On level 6, however, a small northwest fissure zone runs off from 
the west side of the Granite lode about 40 feet north of the point where the Cross 
lode comes in on the east side. It is not clear whether the Cross lode follows the 
Granite lode for 40 feet before resuming its northwest course or whether the two 
northwest sheeted zones are really distinct. It is not likely that the offset of 40 
feet is due to faulting of the Cross by the Granite lode, for the latter zone of sheeting 
does not perceptibly fault the granite-breccia contact just north of this point. On 
level 7 the Cross lode is known only on the east side of the Granite lode, and ^n level 
8 it does not appear to have been recognized. On levels 9 and 10 the Cross lode is 
fairly distinct and extends across both the Granite and the West lodes. These facts 
lend additional support to the view that the Cross vein, so called, above level 7 is 
not identical with the Cross lode of levels 9 and 10. 

There is still a third northwest sheeted zone which has been followed on level G 
in a drift north of the shaft and 40 feet northeast of the Bobtail. It dips 70° SW. 

GEOLOGICAL FEATURES. 

While the Granite mine is chiefly in the familiar porphyritic granite exposed 
about Victor, the north end of the mine, including the entire shaft, is in breccia. 
The granite-breccia contact is cut in the main drift at distances ranging from 120 
to 225 feet south from the shaft. The rocks for several feet on each side of the 
contact are usually rather decomposed and show considerable oxidation, even on 
level 10. The general strike of the contact seems to vary from northwest to west, 
but, as there are no drifts on it, this point can not be accurately determined. The 
general dip is northerly, at about 80°. The contact surface, however, is evidently 
very irregular, and there may be local southerly dips between levels 6 and 7 and 
between levels 9 and 10. 


BATTLE MOUNTAIN MINES, WEST GROUP, AND OUTLYING PROSPECTS. 473 

West of the shaft, along the western edge of the claim, a mass of latite-phonolite 
is exposed in the crosscut and drift connecting with the Dead Pine mine. This is 
undoubtedly the same intrusion as that in the northeastern part of the Dead Pine, 
noted on page 485. Its form is unknown, as its contact with the breccia is exposed 
at only one point, on level 6, and is there greatly obscured by alteration and pyritic 
mineralization. 

The granite is cut by several very irregular dikes and sills of phonolite—often 
mere bunches which can not be followed for any great distance, though if completely 
explored the}” would probably be found to connect with small dikes below. At 
the south end of level 10, about 900 feet south of the shaft, is a generally east-west 
dike which is probably continuous with the east-west dikes of the Dillon and Dead 
Pine mines. This dike varies in width from 10 to 30 feet, and is here apparently 
nearly vertical. On its north side it connects with a thick sill-like mass, apparently 
of no great horizontal extent. This sill dips gently south. It lies in the general 
line of the Granite lode and contains an ore body which will presently be described. 
On the same level, about 450 feet south of the shaft, in the vicinity of the Cross 
lode, is another mass of phonolite, lying along the eastern side of the Granite lode. 
This is about 40 feet wide and is apparently a north-south dike. It may continue 
southward and join the sill just described, but the intervening ground is unexplored. 
Toward the north it seems to contract in width and is probably represented by a 
dike about 7 feet wide, which crosses the main drift with a northwesterly course 
about 100 feet south of the shaft. On the levels above the tenth a few irregular 
bunches of phonolite have been discovered in following the lodes, but no regular or 
persistent dike is known. 

The same basic dike known in the Monument and Dillon mines (pp. 475, 476) 
continues through the Granite with a general course of X. 20° W. It passes on all 
levels about 150 feet southwest of the shaft and meets the Bobtail lode, the line of 
junction pitching southeast. On level 6 dike and lode run together for about 50 
feet before they diverge and the dike resumes its usual more northerly course. 
Where the “ basalt ” and the Bobtail are together the dike has the usual dip of 
the lode, about 60° to the southwest. This is either a remarkable coincidence or 
else the Bobtail fissure existed prior to the basic intrusion. The lowest dip exhib¬ 
ited by the dike elsewhere on this level is 70°, also to the west. On the whole, 
however, it is practically vertical, as shown by its relative positions on successive 
levels. The dike suffers no apparent deflection in passing from the granite into 
the breccia. 

CHARACTER OF ORE. 

The ore of the Granite mine is in part metasomatically altered granite similar 
to that described in the Ajax and Portland mines. The best ore being mined at 
the time of visit, however, occurred in phonolite, as little stringers rarely over 
half an inch in width, consisting of quartz, fluorite, rather abundant pyrite and 
sphalerite, with calaverite and a little molybdenite. A vuggv structure is common, 
many of the little projecting crystals of quartz, fluorite, pyrite, and calaverite being 
coated with chalcedony. The phonolite in the vicinity of the veinlets contains 


474 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


nests of fluorite and abundant finely disseminated pyrite. The gold, however, is 
apparently limited to the veinlets. 

The microscope shows that the molybdenite occurs as a coating or envelope 
about crystals of pyrite. The principal alteration of the phonolite in the vein 
walls consists in the complete change of the pyroxene or amphibole to aggregates 
of pyrite, apatite, and an obscure yellowish-brown material resembling limonite. 
The feldspathic constituents of the phonolite are partly sericitized. 

FORM AND STRUCTURE OF THE ORE BODIES. 

Nearly all of the ore thus far discovered lies south of the granite-breccia con¬ 
tact. A little ore, it is true, has been stoped from the Bobtail for a distance of 150 
feet southeast of the point where the lode meets the basalt dike, but it was of low 
grade. The lode lying northeast of the Bobtail, on the same level, is a well-defined 
sheeted zone carrying much fluorite and pyrite but no ore. Within the granite 
the ore occurs as lodes along sheeted zones, particularly where these cut or follow 
phonolite dikes and as irregular bunches at the intersections of fissures. 

The principal pay shoot is on the Granite lode. Although not continuously 
stoped, this pay shoot may be considered as extending from a point about 100 feet 
above level 5 down to level 9. Below level 9 the ore apparently left the Granite 
sheeted zone and followed a branch or intersecting lode, with a westerly dip of about 
60°. On level 10 the same lode lies between the Granite and West lodes. Owing 
to its relatively flat westerly dip, it joins the Granite lode between levels 9 and 10. 

The main Granite pay shoot reaches its greatest development between levels 
6 and 7, with a maximum length of about 350 feet. Above level 7 the general 
pitch of the pay shoot is northerly, while below this level it is southerly. Seen in 
longitudinal section the ore body is rudely crescentic in outline, with the horns of 
the crescent turned south. Above level 8 the ore is said to have terminated north¬ 
ward at the granite-breccia contact. 

While the Granite lode is generally a narrow sheeted zone of the usual type, 
at certain points the ore has been stoped to widths of 30 or 40 feet. On level 6 the 
widest ore occurred close to the contact of the granite with the breccia, where some 
additional fissures join the Granite lode from the north-northwest. On level 7 the 
largest body was at the intersection of the Granite and Cross lodes, the ore narrowing 
from a maximum width of 40 feet at the Cross lode to a few inches near the contact. 
In all cases unusual width of ore in the Granite lode is associated with the inter¬ 
section or junction of the main lode with minor fissures. Bodies of good ore fre- 
cpiently occur where the sheeted zone cuts through a mass of phonolite, as on level 9, 
about 400 feet south of the shaft. 

At the time of visit most of the ore was coming from the southern part of 
level 10, where a north-south sheeted zone which may prove to be the continuation 
of either the Granite or the East lode traverses the irregular sill-like offshoot from 
the east-west phonolite dike. This ore is from 8 to 9 feet in width. The lode 
consists of two small, approximately parallel vuggy veinlets of quartz, about 8 feet 
apart. Between these the phonolite is rather irregularly fractured and seamed 
with minute stringers of quartz and fluorite. The value of the ore lies in these 


BATTLE MOUNTAIN MINES, WEST GROUP, AND OUTLYING PROSPECTS. 475 

major and minor veinlets, which carry sylvanite or calaverite, associated with 
pyrite and a little sphalerite. The tellurides are not always visible. They occur 
most abundantly in the two main fissures. M«re or less p} 7 rite occurs disseminated 
through the rock of the lode and as small stringers and bunches. It is said to contain 
no gold. This ore bod} 7 was of comparatively recent discovery at the time of visit, 
and had been stoped for a length of only 25 or 30 feet. 

The west lode on levels 6 and 7 is a barren sheeted zone in granite. On level 
8, however, a good body of ore has been stoped from this lode for a length of about 
150 feet. The best ore occurred in the northern part of the pay shoot, where some 
phonolite occurs in the line of Assuring. At the north end of the shoot several 
minor fissures intersect the main lode and are accompanied by a local widening of 
the ore. Similar ore bunches occur on levels 9 and 10, where the West and Cross 
lodes intersect. 

The Cross vein contained a body of ore lying chiefly on the southeast side of 
the junction of this lode with the granite lode and extending from level 6 to a point 
about 40 feet above level 5. The maximum length of this pay shoot was about 
150 feet. A small body of ore has also been stoped on level 10 from the Cross lode 
for a short distance on each side of its intersection with the West lode. 

UNDERGROUND WATER. 

While the original water level in the Granite was probably, as in the Portland, 
at about 9,452 feet above sea, or 688 feet below the collar of the shaft, the mine has 
been drained by the deeper workings in the vicinity and is now dry. 

MONUMENT MINE. 

INTRODUCTION. 

The Monument mine, owned by the Monument Gold Mining Company, of Colo¬ 
rado Springs, capital, $300,000, adjoins the Dillon on the north. It, too, is a small 
mine, the underground workings being confined to the narrow and very irregular 
area in the Monument claim that is not covered by older locations. It is almost 
completely inclosed by the Granite claim on the west, the Portland property on the 
north and east, and the Dillon claim on the south. The company was incorpo¬ 
rated in 1898 and has operated the mine under the leasing system. 

UNDERGROUND DEVELOPMENT. 

Access to the mine is through a vertical shaft about 550 feet in depth. There 
are six levels at various distances apart. 

LODE SYSTEMS. 

As in the Dillon, there are a number of narrow sheeted zones of no great width 
or persistency. The Monument lode lies west of the shaft and runs nearly due 
north and south. It dips about 80° E. About 150 feet north of the shaft it is 
joined on the east side by the Kurtz vein, which strikes northwest and dips about 


476 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


70° SW. Neither lode has been followed for more than a few feet north of the junc¬ 
tion. About 200 feet south-southwest from the shaft, near the northwest corner 
of the Dillon claim, is the Par Value vein, which strikes N. 8° W. and intersects the 
Stonehouse lode. In general there are in the mine two intersecting sets of fissure 
zones, one striking a few degrees west of north, represented by the Monument and 
Par Value lodes, and one striking nearly northwest, represented by the Kurtz and 
Stonehouse lodes. The Kurtz lode has not been identified below the 285-foot level. 

GEOLOGICAL FEATURES. 

The general country rock of the Monument is the same granite that occurs in 
the Dillon and Strong mines. The same “basalt” dike noted in the Dillon (p. 477) 
passes through the Monument workings west of the shaft, running nearly parallel 
with the Monument lode. No phonolite dikes were noted in the workings, but the 
dike which occurs in the Dillon east of the shaft (p. 477) may, perhaps, be cut in the 
eastern part of the 309-foot Monument level. No attempt was made to determine 
this point at the time of visit. 

FORM AND STRUCTURE OF TIIE ORE BODIES. 

The ore of the Monument occurs as short pay shoots in bodies which are struc¬ 
turally narrow mineralized sheeted zones in the granite. The sheeted zone of the 
Monument vein is from 3 to 4 feet wide, but has produced very little ore. The 
Kurtz lode, however, which is similar in structure, contains good ore above the 285- 
foot level and has been stoped for a length of P25 feet on the 207-foot level. It is 
noteworthy that very little ore has been found at the junction of the Kurtz and 
Monument lodes, the ore on the Kurtz usually beginning a few feet away from the 
Monument. The Kurtz pay shoot is the longest known in the mine. On the 475- 
foot level a narrow pay shoot ha: been stoped for about 100 feet on a sheeted zone 
which lies 70 feet west of the shaft between the Monument and Par Value lodes and 
strikes N. 17° W. This zone of Assuring is apparently not known on the level above. 
Near the south end of this same level another pay shoot occurs in the Par Value 
lode, extending north and south for 20 to 25 feet from the intersection of this lode 
by the Stonehouse. 

CHARACTER OF ORE. 

There was no opportunity at the time of visit for studying typical exposures 
of the ore. Although no good specimens were seen, the original ore probably con¬ 
sists of sylvanite or calaverite deposited in the crevices of the fissure zones. It is 
usually more or less oxidized. 

DILLON MINE. 

INTRODUCTION. 

The Dillon is a small mine situated near the northeastern limit of the town of 
Victor. The Dillon claim lies immediately west of the Strong and east of the Gran¬ 
ite claim. It is cut into by some of the older claims of the Portland company, par- 


BATTLE MOUNTAIN MINES, WEST GROUP, AND OUTLYING PROSPECTS. 477 

ticularly by the Black Diamond, which divides it into north and south portions. 
The underground workings are all in the irregular fractional part of the claim lying 
north of the Black Diamond. The mine is worked by lessees. 

UNDERGROUND DEVELOPMENT. 

The Dillon workings comprise a vertical shaft about 800 feet in depth, with 
eight short levels. The main drifts, as a rule, run a little west of north and east of 
south. The longest drift is about 450 feet, on level 8, which has been run south¬ 
ward into the Black Diamond claim. 

LODE SYSTEMS. 

There is no dominant or persistent lode known in the Dillon mine, unless a 
phonolite dike east of the shaft, which carries bunches of ore, may be so called. 
The chief characteristic of the mine is a number of short, nearly vertical sheeted 
zones in granite, ranging in strike from north to northeast and carrying bunches 
of ore at their intersections or junctions. In this respect the mine resembles the 
Abe Lincoln. (See p. 277.) There are at least four of these sheeted zones exposed 
in the northwestern part of level 3. The westernmost, known as the Stonehouse 
vein, strikes northwest, seems rather more persistent than the others, and is known 
in the Monument mine. 

GEOLOGICAL FEATURES. 

The general country rock of the Dillon is the familiar porphyritic granite of 
this vicinity, cut by dikes of phonolite and basalt. One phonolite dike striking 
about X. 15° W., and with variable but, on the whole, nearly vertical dip, lies about 
75 feet east of the shaft. The width of this dike varies from 6 to 8 feet. There 
is also an east-west dike with northerly dip, lying south of the shaft and well ex¬ 
posed on level 7. This is very probably the same phonolite dike known in the 
southern parts of the Granite and Dead Pine mines. (See pp. 472 and 485.) 

The Dillon shaft was sunk on a basalt dike which strikes X. 20° W. The 
dike, on the whole, is about vertical, though on some of the levels it lies as much 
as 10 feet on one side or the other of the shaft. It is usually from 2 to 3 feet in 
width and is soft and decomposed. 

FORM AND STRUCTURE OF TIIE ORE BODIES. 

The ore of the Dillon occurs in irregular bunches in and alongside the phono¬ 
lite dike east of the shaft and in the short sheeted zones in the granite of the north¬ 
western part of the mine. The ore occurs chiefly in bunches at the intersections 
of these lodes, and has been found mainly above level 3. The ore associated with 
the phonolite dike does not apparently follow any very distinct sheeted zone, but 
occurs at points where local irregular fracturing has provided spaces in the phono¬ 
lite or adjacent granite for the deposition of tellurides. 


13001 — No. 54—06 - 32 



478 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


AJAX MINE. 

INTRODUCTION. 

The Ajax mine is on the south slope of Battle Mountain, just north of and over¬ 
looking the town of Victor. It is owned by the Ajax Gold Mining Company, of 
Denver, capitalized at $1,500,000, and embraces the Apex, Monarch, Mammoth, 
Pearl, Champion, June Blizzard, Victor Consolidated, Victor Consolidated No. 2, 
Hallett & Hamburg, Necessity, Orpha Nell, Jolly Tar, Lucky Dick, and Gee Mima 
claims. Operations were begun in 1895 and have been continued steadily to date. 
Like the Portland, it is situated on the contact between the granite and the vol¬ 
canic breccia and has extensive workings in both rocks (PI. V, p. 26). On the 
northeast the Ajax ground adjoins the Portland and on the east and southeast 
the Dead Pine property. The mine is well equipped and employs about 140 men. 
Statistics of production and dividends are not obtainable. 

UNDERGROUND DEVELOPMENT. 

The main Ajax shaft, 1,228 feet in depth, is situated near the southern edge 
of the property. The collar is in breccia, but the shaft enters the granite between 
levels 1 and 2 and continues in that rock to the bottom. Connected with this 
shaft are eleven main levels, whi.li, with the exception of levels 4 and 5, are about 100 
feet apart. Level 1 is about 125 feet below the collar of the shaft, and level 5 is 
about 75 feet below level 4. In April, 1904, the drifts and crosscuts cn all levels 
had a total length of 36,143 feet, and the stopes a total volume of 2,020,669 cubic 
feet. The more important workings fall into two main groups—a very irregular 
maze of drifts and stopes in the granite, mostly southwest of the shaft, and a series 
of linear drifts and stopes along two principal fissure zones in the breccia north of 
the shaft. The latter workings pass under the western part of Battle Mountain 
and connect on level 5 with the Battle Mountain tunnel opening into Arequa Gulch, 
between Eclipse and the Economic mill. Level 1 also connects with a long adit 
called the Ithaca tunnel, which has its portal about 500 feet southwest of the Ajax 
shaft, in the gulch between Scpiaw and Battle mountains. 

LODE SYSTEMS. 

The dominant fissure zones in the Ajax mine strike about N. 30° W., running 
general^ parallel with a number of phonolite dikes. Fissures and dikes dip south¬ 
west, as a rule, at angles near 70°. The principal lode is the Apex, which should 
outcrop along a line connecting the McKay shaft, near the northwest corner of the 
Dead Pine claim, with the Victor Consolidated shaft, near the north end of the 
claim of the same name. The Apex lode accompanies a phonolite dike and dips 
southwest at an average angle of 72°. 

About 400 feet northeast of the Apex vein is a second zone of nearly northwest- 
southeast fissures which have produced some ore and are supposed to represent 
the northwesterly continuation of what is known as the Bobtail vein in the Granite 


BATTLE MOUNTAIN MINES, WEST GROUP, AND OUTLYING PROSPECTS. 479 


and Portland mines. (See PI. V, p. 26.) The fissures of this second zone, which 
may conveniently be distinguished as the northeast fissure zone, dip generally to 
the southwest, but in one or two cases exhibit northeasterly dips. Between these 
two main fissure zones occur some hitherto less important lodes ranging in strike 
from north-south to northwest-southeast. These intermediate lodes have not been 
followed for long distances nor shown to contain large ore bodies. 

Lying immediately southwest of the main shaft is a third group of fissures, 
also striking about X. 30° W., forming a zone from 300 to 400 feet in width. These 
fissures dip generally to the southwest at angles ranging from 60° to 80°. 
occur for the most part in granite, just south 
of the granite-breccia contact, and are not 
persistent, rarely maintaining distinct char¬ 
acter for more than 250 feet in length. These 
fissures may collectively he designated the 
southwest zone. 


They 


GEOLOGICAL FEATURES. 

With the exception that latite-phonolite 
has not, so far as known, been encountered 
in the Ajax workings, the rocks of the mine 
are similar to those in the Portland. 

The main contact between the granite 
and the volcanic breccia of Battle Moun¬ 
tain is well exposed on nearly all the levels 
and has in many places been drifted on for 
considerable distances. It is prevailingly 
steep, dipping north or northeast at angles 
ranging usually from 45° to 85°. The aver¬ 
age dip is probably between 70° and 75°. 

Near the shaft, particularly in the upper 
levels, the contact runs nearly east and west. 

But, as is shown on Pis. II (in pocket) and 
V (p. 26), the Ajax shaft is situated in an 
embayment in the granite between the Port¬ 
land promontory (seep. 27) on the east and 
the northward turn of the contact, which 
carries it through the saddle between Squaw 
and Battle mountains, on the west. This 
northerly turn is noticeable on all of the Ajax workings that have followed the con¬ 
tact far enough to the west and is particularly conspicuous on the lower levels. A 
north-south section through the Ajax shaft showing the steep dip of the contact is 
given in fig. 63. The apparent flatter dip below level 6 is partly real and partly 
due to the obliquity of this part of the contact to the plane of the section. 



Fig. 63.—North-south section through the Ajax shaft, 
showing the dip of the granite-breccia contact. 
































480 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

The character of the contact between the granite and breccia, when examined in 
detail, is found to be similar to that described in the Portland. The breccia, contain¬ 
ing abundant fine granitic detritus, fits snugly against a wall of granite, which is far 
too irregular to afford any ground for considering it a fault plane. As in the Port¬ 
land, blocks of granite from 2 to 3 feet in diameter are sometimes found in the breccia 
at a distance of 100 feet or more from the granite in place. The contact is usually 
sharp and definite, though, on account of the granite fragments in the breccia, it is 
not always conspicuous. The granite close to the breccia is seldom breceiated, 
though sometimes considerably jointed and occasionally shattered. 

A basaltic dike, usually from 2 to 4 feet wide, with steep westerly dip, runs 
nearly north and south through the Ajax workings, and is conspicuous on all the 
levels. Above level 3 this dike is practically at the shaft, while on level 10 it passes 
about 100 feet west. It has undergone the usual decomposition and exhibits the 
platy parting parallel to the walls that characterizes the basaltic dikes of the district. 
It cuts squarely across the contact between the granite and the breccia without being 
deflected from its course. While it may practically be considered a single dike, like 
others of its type in the district, it sometimes pinches and is succeeded by a second 
dike lying a few feet to one side or the other of the first, and increasing in width as 
the latter decreases. No ore occurs in the Ajax basaltic dike. 

Many phonolite dikes are encountered in the Ajax, cutting both the granite and 
the breccia. In petrographical character, alteration, and structure they are in every 
way similar to the phonolite dikes of the Portland and other mines in the vicinity. 
They are often exceedingly variable in form, now narrowing or pinching out entirely 
and now branching, widening into irregular masses, or connecting with nearly 
horizontal sheets or sills. Such phonolite dikes as cross the granite-breccia contact 
frequently send off irregular apophyses or branches between the granite and the 
breccia. Most of the dikes, like the lodes, have general northwesterly strikes, but 
some with northeasterly strikes occur in the granite. A few only of the phonolite 
dikes require special mention on account of their relation to the ore bodies. One of 
these is the Apex dike, which accompanies the Apex lode and continues in a south¬ 
easterly direction into the Dead Pine mine, where it is known as the Montana dike. 
This dike, as seen in the Ajax, usually varies in width from 4 to 15 feet, and like 
others of its class is branching and irregular. It forms the hanging wall of the pro¬ 
ductive part of the Apex lode, but in the Ajax mine is not accompanied by any 
important ore bodies along that part of its course which lies in the granite. In the 
Dead Pine and Gold Coin mines, however, it becomes economically important. 

In the granite southwest of the main shaft are some phonolite dikes of general 
northeasterly trend which are related to the large ore bodies of this part of the mine. 
One of these, running almost due southwest from the shaft and dipping about 60° 
NW., is well exposed on level 7, where it is in part mineralized and has been stoped in 
places to a width of 6 or 7 feet. Another smaller dike lying northwest of the last and 
nearly parallel in strike, but with steeper dip, is shown on level 6 passing longitudi¬ 
nally through the great southwest stope in the granite. Possibly there are still 
other dikes comprised in this northeast-southwest zone, but the irregularity of the 
phonolite intrusions and the height of the untimbered stopes preclude the detailed 
tracing out of every dike that may be present. 


BATTLE MOUNTAIN MINES, WEST GROUP, AND OUTLYING PROSPECTS. 481 

On level 4, about 50 feet east of the Ajax shaft, is a north-south phonolite dike 
which forms practically the eastern boundary of a large ore body in granite. The 
same dike also forms the eastern boundary of another ore body lying under the one 
just referred to, or on level 5. 

FORM AM) STRUCTURE OF THE ORE BODIES. 

The greater part of the ore of the Ajax mine is in the granite, occurring, as a 
metasomatically altered and mineralized form of that rock, in large very irregular 
bodies between levels 3 and 8. One of these bodies, on level 4, lies about 100 feet 
northeast of the shaft and has been stoped from north to south for a length of about 
60 feet. Its width is about 30 feet. The ore lies mainly on the west side of a north- 
south phonolite dike and is practically bounded on the north by the granite-breccia 
contact. The altered, mineralized granite which constitutes the ore was irregu¬ 
larly fissured prior to mineralization, the dominant fissures running generally paral¬ 
lel with the phonolite dike. The ore body ends abruptly on the south, not against 
any discoverable fissure, but by a rather rapid change from mineralized to unaltered 
granite. A few irregular fissures continue southward from the ore body into this 
granite. This large ore body has been stoped upward for 50 feet or more, but does 
not appear at all on the level above. Neither does this ore body continue below 
level 4, though another similar body does occur on that level nearly under the stope 
just described. The two masses of ore are separated by barren granite. 

On level 5 the main ore body occurs a little farther west, the shaft penetrating 
its western part. The same phonolite dike noted above here also limits the ore on 
the east, while on all other sides the ore passes irregularly through mineralized 
granite into unaltered country rock. This ore body continues with a southwesterly 
pitch down to a point about half-way between levels 5 and 6, where the ore ends near 
the east side of the basic dike. A short distance west of this dike, however, a third 
ore body was found which on level 6 is rudely elliptical in plan, with its major diam¬ 
eter lying north-northeast and south-southwest. The length of this ore body on 
this level is about 150 feet, and its width about 25 feet. It pitches southwest and 
has been stoped to level 7, where it has a length of about 100 feet and a maximum 
width of about 50 feet. Below level 7 the large irregular mass of ore divides into 
smaller bodies, which though of variable width are so closely related to distinct zones 
of Assuring as to be practically lodes. These lodes will presently be referred to again. 

The great ore bodies in the granite thus occur in a northeast-southwest zone 
passing through the Ajax shaft. Their aggregate length is about 400 feet and 
their vertical range about the same. They pitch generally to the southwest, so that 
the highest bodies occur northeast of the shaft and the lowest bodies southwest of it. 

O 

Below level 8 they are succeeded by narrower deposits of distinctly lode type. 

The occurrence of these large bodies of ore is clearly related to the intersection 
of the two northeast-southwest phonolite dikes by the numerous northwest-south¬ 
east fissures, which has been referred to as the southwest zone, and it is probable 
that this relation is a genetic one and was largely effective in determining points of 
ore deposition within the granite. 


482 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


The lodes in granite, constituting the southwest zone, may be regarded as rela¬ 
tively narrow lateral and downward extensions of the main ore bodies along the 
northwest-southeast fissure zones. These lodes are best developed on level 7, where 
at least three well-marked fissure zones, striking N. 38° W., contain ore to a maxi¬ 
mum distance of about 150 feet northwest from the axis of the main ore body. 
They are rather irregular sheeted zones, usually exhibiting two principal parallel 
fissures 3 or 4 feet apart connected by numerous irregular fractures. The general 
dip is about 70° SW. The ore is usually about 4 feet wide and similar in 
character to much of that found in the large, irregular ore bodies just described. 
The lodes do not have definite walls, the ore passing more or less gradually into the 
granitic country rock. At their northwest ends the pay shoots grade into slightly 
mineralized granite containing little veinlets of pyrite. The Assuring in this direc¬ 
tion becomes less regular and pronounced, and it is doubtful whether at a distance 
of 250 feet from the northeast-southwest phonolite dikes any of the lodes are suffi¬ 
ciently distinct to be recognized in crosscutting. On the southeast side of the large 
ore body these lodes are usually recognizable as rather irregular fissure zones, con¬ 
taining little stringers of pyrite. The} 7 are unimportant on this side of the main ore 
mass and do not contain ore for distances of more than a few feet from the latter. 
Thus practically all the ore in these lodes lies between two divergent vertical 
planes passing through the Ajax shaft, one of these planes striking southwest and 
the other west-southwest. 

On levels 9 and 10, below the bottom of the large southwest ore body, some of 
these lodes have been drifted on, and two of them, probably the two easterly lodes 
known on level 7 as the B and C veins, have proved productive. Their value on 
level 11 is yet to be determined. 

Those productive lodes of the Ajax that occur in breccia have no obvious rela¬ 
tion to the granite-breccia contact, and none of the important breccia ore bodies are 
found in its immediate proximity. No ore is encountered in the Apex lode until a 
point is reached about 450 feet north of the Ajax shaft. Here an ore shoot begins 
which continues northwestward to the Triumph shaft. The maximum length of 
this pay shoot is 500 feet. Its vertical range is about the same, the ore ending just 
above level 4, though the Apex phonolite dike, accompanied by some Assuring, is 
known on lower levels. 

The Apex vein is a sheeted zone in breccia, with an average width of 2 or 3 feet. 
Locally, however, as near an intermediate level about 125 feet below level 1, the ore 
has been stoped to a width of 56 feet. It strikes N. 30° W. and dips 72° SW. The 
Apex phonolite dike, here about 5 feet wide, usually forms the hanging wall of the 
lode, though in places breccia intervenes between the ore.and the dike. In its wider 
parts the lode consists of a number of fissures with considerable barren country rock 
between them. The dominant fissures have the general strike and dip of the lode, 
but others are much less regular. Some, particularly where the ore is widest, 
branch off to the northeast from the main fissures and as they pass into the foot wall 
dip at decreasing angles until they are nearl} 7 horizontal. 

Although the breccia in the vicinity of the lode is generally impregnated with 
pyrite, the ore value is nearly all if not completely in the small fissures, many of 


BATTLE MOUNTAIN MINES, WEST GROUP, AND OUTLYING PROSPECTS. 483 


them only a fraction of an inch in width, which collectively compose the pay shoot. 
The value of the ore thus lies chiefly in the screenings. 

The various smaller lodes in the breccia, such as those of the northeast zone, 
present no structural features of sufficient interest to merit detailed description. 

CHARACTER OF ORE. 

The general types of ore are found in the Ajax mine, one consisting of meta- 
somatically altered granite and the other of sheeted and veined breccia or phonolite. 

The granitic ore has been the more important and is of the same general char¬ 
acter as that found in the Portland, Strong, and Independence mines. Viewed at 
a little distance in the stope walls the ore does not appear very different from the 
unaltered granite and exhibits the usual conspicuous porphyritic structure due to 
the development of phenocrystic aggregates of pink microcline. Closer examina¬ 
tion, however, shows that in the ore all the other principal constituents of the 
granite—namely, the quartz, mica, and oligoclase—have been altered to a porous 
aggregate of adularia, quartz, fluorite, and an obscure green mineral that is prob¬ 
ably roscoelite, as the presence of vanadium is shown by chemical analysis. Pyrite 
occurs in all the secondary minerals and probably calaverite also, though this 
mineral is very difficult to distinguish from the pyrite, as it rarely occurs in large 
crystals. It is said to be sometimes visible in the ore, though none has been iden¬ 
tified with certainty in the specimens collected. The biotite of the granite is the 
first mineral to undergo alteration and is transformed to aggregates of quartz, 
fluorite roscoelite, pyrite, and calaverite. The apatite and zircon of the rock 
appear to be unaffected by the metamorphism. The granitic ore is frequently 
traversed by veinlets filled with pyrite, which so far as known is not auriferous. 
Analyses of the comparatively unaltered granite and of a partly altered specimen 
constituting ore are given below. The two specimens were taken about 1 foot apart. 


Chemical analyses of granite and ore from Ajax mine. 



I. 

II. 


I. 

II. 


66.20 

59.58 

S0 3 . 

None. 

None. 

Alj0 3 .... . 

14.33 

16.00 

Cl. 

Trace. 

(?) 


2.09 

.30 

F. 

(?) 

a.69 

FeO . 

1.93 

.65 


6.12 

c 4 .78 

MtrO . 

.89 

.03 

MnO. 

.13 

Trace. 


1.39 

2.03 

BaO. 

.18 

.11 

NajO 

2.58 

.98 

SrO. 

Trace. 

.01 

KjO . 

7. 31 

11.93 

Li 2 0. 

Trace. 

Trace. 

I1 2 0— ... 

.48 

.32 

V 2 0 3 . 


.39 

h 2 o+ . 

.83 

.81 

M 0 O 3 . 


.01 

Ti0 2 . 

.65 

.75 




Zr0 2 . 

.02 

(?) 


99.74 

99.95 

C0 2 . 

.36 

.26 

Less O lor F. 


.29 

p 2 o 5 . 

.25 

.32 


99.74 

99. 66 


a 1.42 CaF 2 . b 0.067 S. c 2.55 S. 
















































484 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

The specimen of ore analyzed does not represent an extremely altered form 
of the granite, though the biotite is entirely gone. Gold is not estimated, inas¬ 
much as even "2-ounce ore” would contain only 0.006 per cent of the precious 
metal. The occurrence of molybdenum in the ore is noteworthy, the mineral 
molybdenite being apparently almost invariably associated with the telluride ores. 
The bearing of these analyses upon the general subject of the metasomatic changes 
connected with ore deposition has been fully discussed on pages 193 to 195. 

The ore of the breccia commonly occurs in minute veinlets, often showing 
comb structure, and consisting of quartz and fluorite, with pyrite and calaverite. 
Some of the veins contain abundant pyrite, but the abundance of this mineral 
seems to bear no discoverable relation to the richness of the ore. 

The breccia in nearly all parts of the mine, often hundreds of feet from any 
known ore, is abundantly impregnated with pyrite in crystals up to a quarter of 
an inch in diameter. Whereas in the Portland mine the development of pyrite 
in the breccia is usually accompanied by the formation of dolomite, in the Ajax 
country rock the pyrite is associated chiefly with sericite. While it can not be 
said that there has been no carbonization of the breccia in the Ajax mine, yet 
none of the thin sections examined contain noticeable quantities of carbonates. 

Oxidized ores are not a prominent feature in the Ajax mine. Even on the 
125-foot level the oxidation is only partial and on the 400-foot level it is scarcely 
noticeable. 

DEAD PINE MINE. 

INTRODLTCTION. 

The Dead Pine mine, owned by the Ophir Mining and Milling Company, is 
situated on the south slope of Battle Mountain, between the Ajax and Gold Coin 
mines. The workings are confined to the Dead Pine claim, which runs about 
N. 6° E., following the general course of the norther’y continuation of the Coin 
lode. In 1894 the Dead Pine was a mere prospect and received only casual men¬ 
tion in Penrose’s report.® Between 1894 and 1896, however, an inclined shaft 
was sunk on the northern part of the claim and some rich ore stoped in the granite 
near the granite-breccia contact. Later the vertical Oliver shaft was put down 
and is now the main shaft of the mine. 

UNDERGROUND DEVELOPMENT. 

The Oliver shaft is situated 285 feet from the south end of the claim and is 
about 900 feet deep. It is connected with levels at 250, 525, 625, 725, and 825 
feet below the collar. The old Dead Pine incline, 425 feet from the north end of 
the claim, follows the contact between the granite and the breccia, which dips 
70° N. There are ten levels connected with this incline, approximately 50 feet 
apart. The old Dead Pine levels 5 and 9 are connected with the main 250-foot 
and 525-foot levels, respectively. At the south end of the property is another 
inclined shaft connecting with four levels. The second of these is continuous 
with the 250-foot level of the Oliver shaft and is the only level common to all three 
shafts. 


a Mining geology of the Cripple Creek district, Colorado: Sixteenth Ann. Rept. U. S. Geol. Survey, pt. 2, 1895, p. 209. 




BATTLE MOUNTAIN MINES, WEST GROUP, AND OUTLYING PROSPECTS. 485 

The main workings have a generally linear plan and extend longitudinally 
through the claim. Near the old Dead Pine incline, however, are two series of 
northwest-southeast drifts following short cross pay shoots. 

LODE SYSTEMS. 

The fissure zone known in the Gold Coin mine as the Coin vein has an average 
easterly dip at the Gold Coin and Dead Pine line of about 73°. At the Oliver shaft 
the average dip is about 82°. At a point 300 feet north of the Oliver shaft the 
lode is practically vertical, while north of that point the general dip becomes dis¬ 
tinctly westward at an average angle between 80° and 90°. North of the old Dead 
Pine incline the fissure zone passes into the breccia, but becomes very small and 
obscure after leaving the granite. 

In addition to this dominant zone of nearly north-south Assuring, there are in 
the northern part of the mine two zones of cross fissures. The more northerly of 
these zones has a general strike of N. 48° W. The more southerly zone, which 
intersects the main Dead Pine lode about 125 feet south of the other, has a general 
strike of N. 26° W. The two zones thus converge toward the Ajax ground. Both 
fissure zones dip to the southwest—the northern one at 70°, the southern one at 
angles ranging from 35° to 80°, the latter being the usual dip. The southern zone 
is known as the Montana vein and follows the curved and irregular course of the 
phonolite dike of the same name. 

As the granite-breccia contact, which has locally a nearly east-west trend, dips 
to the north, while the northern fissure zone dips to the southwest, the two converge 
upward. The fissure zone, as a consequence of this convergence, meets the con¬ 
tact in the vicinity of the old level 8. If it persists above that level it should pass 
into the breccia, into which, however, it has not been followed. 

There is no perceptible displacement of the lodes at the points where the main 
fissure zone and the cross fissures intersect. 

GEOLOGICAL FEATURES. 

All the ore of the Dead Pine mine occurs in granite or in dikes of phonolite 
cutting the granite. The contact between the granite and the breccia crosses the 
northern part of the workings in a nearly east-west direction and dips north at 70°. 
Its position is §hown by the old Dead Pine incline, which follows the contact. The 
latter is fairly sharp and usually accompanied by some pyritization of the neigh¬ 
boring breccia. A few crosscuts have been run into the breccia without, however, 
the discovery of anything of value. The long crosscut on the 625-foot level to the 
northeast corner of the claim passes through breccia into massive latite-phonolite. 

The granite of the Dead Pine is the same as that forming the principal country 
rock of the Gold Coin, Granite, and Strong mines and needs no further description. 

The two principal phonolite dikes are the Montana dike and the East-West 
dike. The former is probably a continuation of the Montana dike of the Gold Coin 
mine and passes northwestward into the Ajax ground, where it is known as the 
Apex dike. It appears to divide as it crosses the Dead Pine and Ajax line, sending 
off a northerly branch toward the McKay shaft near the northwest corner of the 


486 GEOLOGY AND GOLD DEPOSITS OF THE CEIPPLE CREEK DISTRICT. 


Dead Pine claim. The dike itself is so irregular, however, in the vicinity of the 
granite-breccia contact, and there are so many other small intrusions of phonolite 
in the granite, that it is impossible to trace its exact course without actually drifting 
on it. On the old level 8, for example, there is a small curved east-west dike, just 
south of the incline, which probably joins the Montana dike to the west, and 200 
feet southwest of the incline is a nearly north-south dike which probably joins the 
Montana dike to the south. In the southern half of the Dead Pine claim the 
Montana dike has not been exposed, though it can not lie very far east of the main 
drift on the 825-foot level. It probably has here a nearly north-south cQurse. 
North of the Oliver shaft it is visible on the 250-foot level in a crosscut 115 feet 
east of the main lode. From this point it swings northwestward, crossing the line 
of the main lode and continuing into Ajax ground. Its average dip in this part of 
its course is about 80° SW. The width of the Montana dike varies from 10 to 25 
feet. 

The East-West dike crosses the Dead Pine claim at the surface about 75 feet 
north of its south end line. It is usually about 10 feet wider and dips to the north 
at an angle of 65°. It is cut on the 250-foot level 170 feet south of the shaft, on 
the 525-foot level 50 feet south of the shaft, on the 625-foot level at the shaft, on 
the 725-foot level 65 feet north of the shaft, and on the 825-foot level 125 feet north 
of the shaft. 

There are several other small phonolite dikes encountered in the mine, but 
they are less persistent and usually even more irregular than those described. 

FORM AND STRUCTURE OF THE ORE BODIES. 

The principal ore bodies thus far discussed have occurred in the northern part 
of the mine, near the old incline. One of these pay shoots is in the main fissure 
zone, between the Montana dike and the granite-breccia contact, and attains its 
maximum development on the old level 5, or 250-foot level of the Oliver shaft. 
This is a narrow sheeted zone in granite similar in character to the short lodes 
occurring in connection with the large southwest ore body of the Ajax mine. 
Another ore body has been stoped in the more northerly of the two cross lodes. 
This pay shoot begins just above the old level s and has been stoped down to the 
old level 10. On the old level 11, or the present 625-foot level, the ore becomes 
too narrow to stope. This ore body was rarely over 3 feet wide and probably 
nowhere more than 50 feet in length. 

Between the 250-foot and 725-foot levels bunches of good ore occur on one or 
both sides of the Montana dike at the intersection of the dike of the main Dead Pine 
fissure zone (fig. 19). A few small bodies of ore have also been found at other 
points along the contacts of the Montana dike with the granite, but these have 
been of little importance. 

No pay shoots have yet been found in the Dead Pine lode between the Montana 
dike and the East-West dike. Throughout this part of its course the lode is a well- 
defined sheeted zone in granite, occasionally passing through small, irregular dikes 
of phonolite. Some of these dikes have a general north-south course and are occa¬ 
sionally followed for a hundred feet or more by the fissure zone, as may be seen on 


BATTLE MOUNTAIN MINES, WEST GROUP, AND OUTLYING PROSPECTS. 487 

the 250-foot level. On most of the levels the fissuring is rather irregular near the 
point where the lode changes from an easterly to a westerly dip, but there is nothing 
to indicate any break in the general continuity of the Dead Pine lode. 

South of Die East-West dike a few small disconnected bunches of ore have been 
found in the Dead Pine lode on the 525-foot and 825-foot levels. Near the Gold 
Coin line the ore has been stoped to a maximum width of 5 feet and to a height of 40 
feet above the 825-foot level. At this height the fissure zone shows considerable 
oxidation and no longer contains paying ore. Although the stopes of the Gold 
Coin come practically up to the Dead Pine line on nearly all levels, there is no sharp 
change in the character of the ore precisely at the line. The difference in develop¬ 
ment in the two mines merely indicates that the Gold Coin mine was able, in connec¬ 
tion with its higher-grade ores, to carry its stopes into ore of somewhat lower grade 
than the Dead Pine mine can profitably handle. 

CHARACTER OF ORE. 

None of the ore formerly mined in the old north workings was seen at the time 
of visit. It contained tellurides from which the gold had been partly freed by 
oxidation. In its general character it probably differed in no essential degree from 
the ore found at the same depth in the granite of the Ajax mine. The ore of the 
825-foot level occurs as a telluride—probably calaverite, with quartz and fluorite 
within the small fractures in the granite which accompany the dominant fissure of 
the lode. The vein minerals occur in the usual manner as a drusy incrustation on 
the walls of the narrow fractures. In the main fissure zone there is usually present 
a streak an inch or two wide, commonly termed “block quartz,” which is used as an 
indicator in following the lode. This streak is chiefly fineh r crystalline quartz which 
apparently owes its dark line to the presence of minute crystals of pyrite. It some¬ 
times has an open or cellular structure and may then contain calaverite, or, if partly 
oxidized, calaverite and free gold. 

VALUE OF THE ORE. 

Little could be learned at the time of visit of the range in value of the ore 
stoped in the northern and hitherto most productive part of the mine. Portions of 
the main lode on the 825-foot level contain as much as 2 ounces of gold to the ton, 
but the average tenor of the ore now stoped is probably below this. Ore worth less 
than 812 per ton can not at present be profitably handled. 

GOLD COIN MINE. 

INTRODUCTION. 

The Gold Coin mine is owned by the Gold Coin Mining and Leasing Company, 
incorporated in 1895 with a capital of 81,000,000. It is situated in the town of 
Victor adjoining the south end of the Dead Pine mine, and includes the Gold Coin, 
Little Montana, Golden Discovery, and other claims. Its shaft house, built to' 
replace one burned in 1897, is substantially constructed of brick, and is the best 
building of its kind in the district. The company also operates the Economic mill 


488 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 


in Eclipse Gulch, the ore and waste being all hauled by an electric locomotive 
through the Columbine tunnel, about three-fourths of a mile in length, which passes 
under Squaw Mountain and connects the mine and mill. Both ore and waste are 
hoisted to the surface and distributed to chutes which convey it to the bins on the 
tunnel level. The company began operations on the Gold Coin claim in 1895 and 
encountered ore the following year. The mine has since been producing steadily. 

UNDERGROUND DEVELOPMENT. 


The mine is worked through the Gold Coin vertical shaft, situated nearly in the 
center of the Gold Coin claim, and a little over 1,200 feet in depth. There are twelve 
main levels at rather irregular distances apart. Of these level 1 is now used merely 

as a connection with the Columbine tunnel, 
while level 2 was never of much importance, 
the stopes having been carried up continu¬ 
ously from level 3 to level 1. The important 
workings all lie north of an east-west line 
drawn 200 feet south of the shaft, and are of 
general linear plan, following the nearly north- 
south Coin vein. In addition to the main 
drifts on the Coin lode, there are some im¬ 
portant series of divergent and parallel drifts, 
as will appear in the descriptions of the lode 
systems. Level 12 was under water at the 
time of visit. Several of the levels connect 
directly with the workings of the Dead Pine 
mine on the north. The shaft is in the foot 
wall of most of the lodes, which are reached 
on all levels by a main easterly crosscut. 
About 1,100 feet a little east of south from 
the Gold Coin shaft is the old Providence 
shaft, which connects with a long south drift 
on the Gold Coin level 6. 

LODE SYSTEMS. 

The principal lode (fig. 64) is the Coin, 
striking about N. 8° W., and dipping to the 
east. Near the shaft the average dip is about 
83°, while near the north end of the mine 
this is reduced to 70°. 

East of the Coin lode is the Montana lode, following the Montana phonolite dike. 
On level 5, at the latitude of the shaft, the Montana lode is about 240 feet east of the 
Coin lode. It has an easterly dip of about 74° and thus lies farther and farther east 
of the Coin on successive lower levels. The general strike of the Montana lode is 



Fig. 64.—Plan of level 7, Gold Coin mine, showing 
vein system. 







BATTLE MOUNTAIN MINES, WEST GROUP, AND OUTLYING PROSPECTS. 489 

N. 20° W., in consequence of which it approaches the Coin lode toward the north, 
and, were this trend maintained, would meet it on level 5, near the old south incline 
on the Dead Pine claim. 

In the angle between the Coin and Montana lodes are two lodes—one nearer the 
Montana, known as the No. 3 vein, anti one nearer the Coin lode, variously known 
as the Parallel or Spur vein. The Spur vein has a general strike of N. 20° W., run¬ 
ning about parallel with the Montana lode. The dip is northeast at an average 
angle of about 62.° This lode was first clearly recognized on level 4, where it lies 
only about 25 feet east of the Coin lode, to which it is locally nearly parallel. It 
was from this fact, before its general divergent relation was discerned, that it 
received the name of the Parallel vein. The Spur lode joins the Coin lode, the line 
of junction pitching north at an angle of about 50° from the horizon. 

The No. 3 vein is a small lode with the same general strike as the Spur and 
Montana lodes. Its dip, however, unlike those fissures, is westerly, at an angle of 
nearly 80°. This lode is not distinct on level 5, but is known on levels 6, 7, and 8. 
Below level 8 the No. 3 lode joins the Spur vein. 

West of the Coin lode and passing close to the shaft is the Dorothy lode, first 
recognizable on level 9 and continuing through all the lower levels. The Dorothy 
strikes N. 7° W., being thus essentially parallel with the Coin lode. • The dip is 
practically vertical. Very little is known of the Dorothy lode south of the shaft. 
The development has been almost entirely northward. 

The Cashen lode, the principal fissure.zone of the Mary Cashen mine, conies 
into the Gold Coin ground, east-northeast of the shaft, on the eastern side of the 
Montana dike and has been worked from levels 6 and 7. It strikes about N. 18° 
E. and dips at an angle of 70° W. So far as known, the lode does not cross the 
Montana dike. 

About 60 feet east of the Coin lode the main crosscut on level 4 passes through 
a closely spaced sheeted zone with steep easterly dip and nearly north-south strike. 
What is perhaps the same fissure is cut in an east crosscut about 400 feet south of 
the shaft and about 100 feet east of the south drift. At this point a strong stream 
of water issues from the fissure zone. In the northern part of the same level are 
several fissures lying east of the main Coin drift and perhaps representing the north¬ 
ward continuation of the fissure zone just described. One of these fissures at a 
point about 100 feet south of the Dead Pine line and 30 feet east of the main Coin 
drift has lately been found to contain a bod}” of ore. 

There is still another fissure zone in the Gold Coin mine, which, while it nowhere 
contains ore, appears to have had some influence on ore deposition. It has some¬ 
times been called the Cashen vein, but is an entirely different fissure zone from the 
Cashen lode proper. As it shows unmistakable evidence of fault movement, it may 
be conveniently distinguished from the Cashen lode by referring to it as the Cashen 
fault. The general strike of this zone of Assuring is N. 20° E. It dips northwest at 
an average angle of 51°. On the fifth and higher levels the Cashen fault lies to the 
east of the present workings. On level 6 it is probably cut by the Montana dike, 
though no particular examination was made to determine this point at the time of 
visit. On the same level a long east crosscut south of the Providence shaft passes, 
about 75 feet from the drift, through a strong zone of Assuring which is probably 


I 


490 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

the Cashen fault. On level 7 the Cashen fault is well shown in the main east cross¬ 
cut, about 60 feet west of the Montana dike, and may also be seen in the drift follow¬ 
ing the dike. Level 8 apparently does not go far enough east to cut the fault, but it 
shows on level 9 in the main east crosscut about 35 feet east of the Coin lode and also 
in the drifts on the Coin and Spur lodes. On level 10 the fault is cut in the main 
crosscut about 90 feet east of the shaft and also near the end of a west crosscut about 
400 feet south of the shaft. At the latter place the fault is apparently represented 
by a number of nearly parallel fissures forming a zone nearly 50 feet in width. On 
level 11 the Cashen fault should be very near the main shaft, but its exact position 
was not determined. 

GEOLOGICAL FEATURES. 

The general country rock of the Gold Coin mine is the porphyritic granite which 
underlies the town of Victor and occurs in the Dead Pine, Ajax, Strong, and other 
mines in the vicinity. This is cut by several irregular dikes and sills of phonolite 
and by one small basaltic dike. The principal dike is the Montana, which is fol¬ 
lowed by the Montana lode. This dike varies in width from 10 to 40 feet. Another 
small dike, rarely over a foot in width, appears at intervals along the sheeted zone 
constituting the Dorothy lode, and a similar narrow and irregular dike of phonolite 
occurs along the No. 3 lode. 

Irregular sheets or sills of phonolite occur in several parts of the mine, and are 
usually connected with dikes. The manner in which a dike may locally turn into 
a nearly horizontal sill is well illustrated in the long west crosscut from the Coin drift, 
about 500 feet north of the shaft. Here a dike about 1 foot wide, with steep easterly 
dip, turns sharply west for about 6 feet, forming a nearly horizontal sill about 6 
inches thick. It then again bends down into a dike 16 inches in width, dipping 
steeply to the west. Another good example may be seen at the north end of level 4, 
where a dike along the Coin lode, instead of continuing down below the drift, turns 
off to the east as a flat sill. These occurrences show that the phonolitic intrusions 
in the granite are far from regular, and that it can not be assumed that either dikes 
or sills maintain their courses for long distances through unexplored ground. 

The most important phonolite sheet or sill in the mine is that exposed in level 
6, along the drift on the Spur lode. This sill, from 6 to 10 feet thick, is rolling and 
irregular, but has a gentle easterly dip which carries it about 40 feet below the level 
at the point where the main crosscut crosses the No. 3 lode. About 60 feet farther 
east, however, the top of a body of phonolite, probably an anticlinal roll of the same 
sill, is exposed in the bottom of the crosscut. Still farther east the sill probably 
connects with the Montana dike. All the phonolite seen in the Gold Coin mine is 
the usual aphanitic, greenish-gray, altered variety commonly occurring in dikes 
and sills throughout the district. 

The only basic dike seen in the mine is exposed near the face of a west crosscut 
from the north Coin drift on level 5. It is about 7 inches wide, strikes nearly north 
and south, and dips about 60° W. It is soft and decomposed and of no economic 
importance. 

The only fault of importance recognized in the mine is the Cashen fault. The 
productive lodes are generally sheeted zones showing little evidence of differential 


I 


BATTLE MOUNTAIN MINES, WEST GROUP, AND OUTLYING PROSPECTS. 491 

movement of the walls, but the Cashen fault is characterized by the presence of more 
or less crushed and decomposed country rock or gouge. This material is sometimes 
4 or 5 feet in width. The net displacement effected by this movement, which may 
have been oscillatory, does not appear to have been great, as the fissures containing 
ore on the northwest side of the Cashen fault can in some cases be followed on its 
southeast side and show no appreciable offsetting at the lines of intersection, and 
the Montana dike is not noticeably offset where crossed by the Cashen fault on level 
7. As most of the lode fissures meet the Cashen fault at an oblique angle, however, 
the throw of the Cashen fault, assuming it to be later than the formation of the other 
fissures, is not readily detected. On the other hand, the fault may be older than the 
fissures that cross it. No decisive structural evidence bearing on this question was 
discovered, though the occurrence of the ores affords, as will presently be seen, some 
ground for thinking this explanation the true one. Its acceptance leads to certain 
corollaries in the shape of suggestive hypotheses as to the source and direction of 
movement of the ore-bearing solutions or gases. 

FORM AND STRUCTURE OF THE ORE BODIES. 

With the exception of some small bodies of ore stoped above level 6 near the 
Providence shaft, in the southern part of the mine, all the ore bodies lie in the 
northern half of the property. This productive ground extends from a point about 
300 feet south of the main shaft northward to the Dead Pine line—a distance of 
about 900 feet. The Cashen fault is the dividing plane between the generally 
productive and generally nonproductive territory. On the northwest or hanging- 
wall side of this fissure zone lie all of the productive portions of the Dorothy, Coin, 
Spur, No. 3, and Montana lodes. The ore bodies are without exception typical 
lodes determined by relatively narrow individual zones of sheeting or by the coales¬ 
cence of such narrow zones into pay shoots of considerable local width. 

The Dorothy lode, as seen on levels 9, 10, and 11, is a distinct sheeted zone in 
granite, usually from 3 to 4 feet wide, but without regular or persistent walls. There 
are usually two fairly regular narrow cracks or fissures which contain the bulk of the 
ore, the rest of the lode being made up of less regular fractures containing relatively 
little value. The stopes rarely exceed 4 feet in width, though in one or two cases 
little flat seams of ore have been followed for a few feet into the east wall. A 
narrow phonolite dike usually accompanies the lode, although the two are not 
always coincident. When the fissure zone does actually follow the dike the ore is of 
lower grade than when the lode is wholly in the graniter. The stopes extend only a 
short distance above level 9, the Assuring becoming irregular and indistinct as it is 
followed upward. On level 8 the Dorothy has not been clearly identified, though it 
may be represented by some indistinct Assuring about 50 feet east of the shaft. 
Toward the north the pay shoot usually comes to an end with the appearance of the 
phonolite dike in the Assure zone, a diminution of the Assuring, and a gradual 
decrease in the value of the ore. The Assuring also becomes less pronounced and 
the ore of lower grade near the main shaft. 

The Coin lode has been stoped almost continuously from the surface to level 9 
and between the main shaft and the Dead Pine line. This pay shoot seems to have 



492 GEOLOGY AND GOLD DEPOSITS' OF THE CRIPPLE CREEK DISTRICT. 

reached its maximum length of about 850 feet on levels 5 and 6, where it extended 
nearly 250 feet south of the shaft. Below level 9 only small isolated bodies of ore 
have yet been found in the Coin lode, though a new ore body has recently been opened 
near the north end of level 10 in a fissure zone lying parallel with and about 30 feet to 
the east of what had hitherto been considered the Coin lode. Whether this is really 
the Coin or a new lode not known on the levels above could not be ascertained in the 
stage of development reached at the time of visit. The general dip of the Coin lode, 
however, as shown in the levels above the tenth, should bring the lode rather nearer 
to the new ore body than to the old north drift on what was formerly considered the 
Coin lode on level 10. The lode is a mineralized sheeted zone in granite, the average 
width of the zone of distinct sheeting being probably about 4 feet. The zone usually 
consists of two narrow, fairly regular fissures about 4 feet apart, between which are 
other nearly parallel fissures, usually less regular and persistent, and numerous 
minor linking fractures. The stopes are often considerably wider than this, however, 
as the ore is not always limited by the dominant fissures of the zone. Thus on level 
4 the average width of the main stope is probably 10 or 12 feet. The widest stope 
in the mine is near the north end of level 4, where, at the junction of a small branch 
fissure zone with the Coin lode, the ore was 25 feet wide. An unusually wide body 
of ore is commonly found also where the Coin and Spur lodes join. On level 8 the 
Coin pay shoot varies in width from 4 to 10 feet, the average being about 5 feet. 

The Coin lode continues both to the north and south, beyond the points where 
pay ore stops, as a more or less distinct sheeted zone which often shows no visible 
difference from the productive portions. In some cases, however, such barren 
continuations of the lode are irregular and indistinct. 

There was little opportunity in 1903 of examining typical occurrences of ore in 
the Coin lode. The valuable minerals, however, seem to be practically confined to 
the actual fissures, usually less than an inch in width, which make up the fissure 
zone. 

The Spur lode is a mineralized sheeted zone in granite and is of the usual type. 
It has been stoped from level 4 to level 9, the ore body extending from the junction 
with the Coin lode a varying distance to the southeast. Its maximum length 
(about 225 feet) is attained on level 8. On levels 8 and 9 the northeast end of the 
ore bod} r is very close to the Cashen fault. The strike and dip of this fault are such 
as to cause its line of intersection with the Coin lode to pitch northward at a lower 
angle than the line of junction of the Coin and Spur lodes. As a result of this the 
Spur lode, if it is ever identified on level 10, will probably lie within the hitherto 
unproductive ground in the foot wall of the Cashen fault. 

The general structure of the Spur fissure zone is similar to that of the Coin. 
Near level 6, where the Spur lode passes through the phonolite sill already described, 
the ore body contracts in width anti decreases in value. There is no noticeable 
faulting of the phonolite by the lode fissures. 

The No. 3 lode is of the same general type as the Spur, but is narrower, the 
stopes being usually from 3 to 4 feet wide. The fissure zone constituting the lode 
follows in part a small phonolite dike, the presence of which seems to have no appre¬ 
ciable influence on the character of the ore, which occurs mainly in the fractured 


BATTLE MOUNTAIN MINES, WEST GROUP, AND OUTLYING PROSPECTS. 493 

granite. At the main crosscut on level 6, where two or three minor fissures come into 
the No. 3 from the south, there is a local widening of the ore body to nearly 25 feet. 
The No. 3 vein is not known much above level 6, while below level 8 it joins the Spur 
vein, as already described. The pay shoot is rarely over 100 feet in length. Toward 
the southeast the sheeted zone as a rule passes into a few small and irregular fissures 
which become indistinct before reaching the main east crosscut and can not be 
distinguished from the ordinary jointing of the country rock. Unlike the Spur vein, 
the No. 3 where it cuts through the main phonolite sill 30 or 40 feet below level G 
carries good ore in the phonolite, while in the granite just above and just below the 
sill the ore has proved of little value. The lode is less regular in the phonolite, the 
sheeted zone changing to a number of very irregular fractures containing sylvanite 
or calaverite and pyrite. 

The Montana lode is essentially a phonolite dike along which, particularly along 
its contacts with the granite, there has been a little parallel sheeting. Bunches of 
ore have been stoped at various points along the dike, sometimes on one side, 
sometimes on the other, but rarely within the dike itself. On level 9 a good body of 
ore has recently been found at the point where the Cashen lode meets the Montana 
dike. This ore occurs chiefly on the east side of the dike, partly in the phonolite 
and partly in the granite. As a whole, the ore bodies found along the Montana dike 
have not been important. 

The Cashen lode as exposed on levels 6 and 7 is a sheeted zone in granite 
carrying fairly good ore about 8 inches in width. 

CHARACTER OF ORE. 

The unoxidized ores of the Gold Coin mine are mineralogically simple and owe 
their value to the presence of calaverite, with possibly other tellurides not definitely 
recognized, occurring in narrow fissures with drusy incrustations of quartz and 
fluorite. Metasomatic alteration of the kind that has changed extensive bodies 
of granite into ore in the Ajax and Portland mines is practically absent in the Gold 
Coin mine. At distances greater than a few inches from well-defined fissures the 
granite is barren, or at least does not constitute ore. In parts of the Gold Coin 
and Dorothy veins where the sheeting has been intense the vein consists of a mass 
of crushed granite, quartz, fluorite, and small crystals of pyrite. Such ore frequently 
shows no telluride mineral to the naked eye. Sphalerite, though not an abundant 
constituent of the ore, was noted in the Dorothy vein at the 1,100-foot level. At 
one place near the north end of the mine the Gold Coin vein contains a dark brecci- 
ated streak about 4 inches wide, which is veined with quartz and contains dissem¬ 
inated pyrite and fluorite. The microscope shows this material to consist chiefly 
of granitic fragments, but to contain also some fragments of phonolite. These phono¬ 
lite fragments may have been derived from some phonolite dike cut by the fissure. 
The ore occurring in phonolite exhibits the usual character of ores in this rock— 
small crystals of calaverite occurring with druses of fluorite and quartz in very 
narrow joint fissures. The ore in the Gold Coin mine is not extensively oxidized 
below a depth of 650 feet, though partly oxidized ores are found at a depth of 
J ,000 feet. 


13001 — No. 54—06 - 33 



494 GEOLOGY ANT) GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

UNDERGROUND WATER. 

Water was first reached in the Gold Coin mine at a depth of 369 feet or 9,396 
feet above sea level. The maximum flow of 900 gallons a minute was attained at 
a depth of 1,000 feet. In July, 1903, the water was being held 9 feet below the 
1,100-foot level by pumping 740 gallons a minute and by maintaining two bulk¬ 
heads in wet crosscuts on level 10. The pressure on one of these bulkheads was 
93 pounds and on the other 84 pounds, corresponding to heads of about 214 and 
193 feet, or to water surfaces 8,979 and 8,958 feet, respectively, above sea level. 
These conditions had remained unchanged for about a year. 

In October, after the opening of the El Paso tunnel, the pressure on the bulk¬ 
heads began to decrease and in February, 1904, it had fallen to 74 and 68 pounds. 
In March level 12 was recovered by pumping 700 gallons a minute for ten days and 
was then kept open by a discharge of 500 gallons a minute. The bulkheads were 
still left in level 10 and sustained pressures corresponding on April 16 to water 
surfaces about 8,919 and 8,901 feet above sea level, respectively. At this time the 
pumps were raising 490 gallons a minute to keep the bottom level open. 

SUNSET-ECLIPSE MINE. 

The Eclipse, situated at an elevation of 9,700 feet in Eclipse Gulch, just east 
of the Elkton mine, was one of the earliest producers of the district and is briefly 
described by Penrose on page 207 of his report. It is developed by a tunnel at an 
elevation of 9,672 feet and a shaft 500 feet deep situated 70 feet south of the tunnel; 
the* elevation of the collar is 9,689 feet. The Sunset mine, consolidated with the 
Eclipse, is opened by a tunnel at about the same elevation as the Eclipse tunnel 
and about 400 feet south of it. There are also some surface workings on the ground 
of the company on the hill slope north of the Eclipse. The total developments 
amount to several thousand feet. The total production probably exceeds $100,000. 
Water has caused much inconvenience. In March, 1904, the shaft was filled to 
an elevation of 9,465 feet or 224 feet below the collar. Gas filled level 1 so that 
only the tunnel was accessible. The mine was worked in a small way by lessees. 

The country rock is throughout a much oxidized volcanic breccia. The veins 
exposed in the tunnel are as follows: A north-south vein, dipping steeply westward, 
175 feet east of the portal, has been drifted on for a hundred feet north and south 
from the tunnel. The stupes on this vein were 100 feet long, but descended only 
40 feet below tunnel level; the ore was taken out 2 or 3 feet wide and consisted of 
kaolin with pseudomorplis of gold after calaverite. No ore has been found on this 
vein in the lower workings. Forty feet farther east in the tunnel is a flat vein 
dipping 45° or less to the west. This vein is not known below in the Eclipse mine, 
but is prominent in the Carbonate Queen. Ten feet east, of this a third vertical vein 
is cut; this is the only vein which has proved productive in the lower levels of the 
shaft. There are two ore shoots 80 and 40 feet long on it, both of which are said to 
extend down to level 5. A hundred feet north of the tunnel the flat vein, the vertical 
north-south vein, and a vertical east-west vein intersect and here a large shoot of 
ore 90 feet high occurred; it was chiefly, however, confined to the vertical vein 


BATTLE MOUNTAIN MINES, WEST GROUP, AND OUTLYING PROSPECTS. 495 

and did not appear on the lower levels. The Sunset tunnel has opened the same 
vein system, with an additional north-south vein from which some good ore has 
been stoped ; but this part of the property has produced a smaller quantity of ore. 

CARBONATE QUEEN MINE. 

This property consists of a claim adjoining the Eclipse on the east and is owned 
by the Ophir Mining and Milling Company. It is developed by a tunnel entering 
under the Midland trestle, 40 feet above the Eclipse and by a shaft 500 feet deep, 
350 feet east-southeast of the Eclipse shaft, the elevation of the collar being 9,910 
feet. Drifts aggregate about 1,500 feet. No work was done in 1904. The workings 
connect in part with those on the Eclipse. The production is considerable, but the 
exact amount could not he ascertained. The Carbonate Queen has the same flat, 
westward-dipping vein as the Eclipse, and some ore has been extracted from it. 
There is also a north-south vein and several others trending east and west. The 
country rock is breccia. 

BIG BULL, BRIND, AND STRAUB MOUNTAINS AND GROUSE IIILE. 

. Big Bull Mountain is a large flat-topped granite mountain 14 miles east of 
VTctor, rising to an elevation of 10,826 feet. Its northern slope is covered with 
breccia, latite-phonolite, and phonolite. Very few basic or phonolite dikes were 
noted. Regarding the relations of these rocks in depth there is little information, 
except that the contact between breccia and granite is steep in some places at 
least, as for instance at the Safety prospect shaft. 

While there are many prospects scattered over the volcanic areas and a few 
in the granite, there have been no developments of importance thus far and there 
is practically no production. Encouraging assays have been obtained in many 
places. 

Brind Mountain, 10,500 feet above the sea, is situated 1| miles south of Big 
Bull Mountain. Pikes Peak granite is the principal rock. On the north side it is 
cut by a long dike of diabase and by another of phonolite. Some prospecting has 
been carried on in the latter, but so far as known without .valuable result. 

Straub Mountain, the elevation of which is 10,050 feet, lies 14 miles west of 
Brind Mountain. It is covered with the sandy detrital deposits discussed on page 22, 
and in these lie several intruded masses of phonolite. The summit is occupied by 
one of these bodies, in which many prospects have been opened. It is said that 
the phonolite contains low-grade gold ores and attempts were made at one time 
to work these by means of a small cyanide plant situated near the summit of the 
hill. 

Grouse Hill rises to an elevation of 9,800 feet, and is 14 miles west of Straub 
Mountain, from which it is separated by the deep gash of Wilson Canyon. Its 
geological structure is similar to that of the hill just described, though the body 
of phonolite occupying its upper part is very much larger than the'mass on Straub 
Mountain. A great number of prospects are opened on its east and south sides, 
but nothing of well-established value has as yet been encountered. Teals tunnel 


496 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 

has been driven into the phonolite in a westerly direction from the east side. A 
vein which is reported to have given fair assays was encountered 450 feet from the 
portal; in the face the fresh phonolite contains seams of brown jasper inclosing 
purple fluorite. Several prospect shafts have been sunk near the southern edge 
of the phonolite, and some of them have penetrated into the underlying rhyolite. 

In the space between Grouse Hill, Straub Mountain, and the town of Victor 
the granite contains many phonolite dikes, on a number of which prospecting 
has been done. Some of them yielded fair assays and one contained galena, 
but nothing of permanent value has been found. 

LOWER CRIPPLE CREEK. 

The rapidly deepening canyon of Cripple Creek extends southwest from the 
city of the same name, first through Cripple Creek granite and lower down through 
Pikes Peak granite. The slopes and uplands on the west side are practically barren. 
At the junction of Arequa Gulch with Cripple Creek, forming the extreme point 
of Beacon Hill, some evidences of mineralization are seen. The Newell tunnel is 
driven from Arequa Gulch into Grouse Hill; 1,000 feet from the portal a vein is 
reported to have been cut which has been drifted on for 600 feet north and south. 
It appears to follow a phonolite dike and some paying ore is reported to have been 
found, as well as a considerable amount of low grade. The ore contains a little 
galena. The property is owned by the Buffalo and Cripple Creek Gold Mining 
Company. 

One mile farther down the canyon and 34 miles from Cripple Creek a phonolite 
dike, called the Gold Watch vein, crops on the west side in the granite. Early in 
1904 some very good ore was encountered in this dike near the surface. 

About 6 miles down the canyon from Cripple Creek, just outside of the area 
shown on the map, some evidences of mineralization of a different kind are met. 
The elevation is here about 7,700 feet. Outcrops of narrow veins occur on the 
precipitous bluffs of granite and on the summit of the plateau on both sides, about 
2,000 feet above the creek. A tunnel has been started here by the Big Twenty 
Mining Company, and is intended to penetrate the bluff toward the east, with a 
view to opening the veins cropping high above. 

The granite bears evidence of much shearing and crushing, and is intersected 
by aplite dikes. The veins, which course in various directions, are narrow zones 
of sheeting carrying in places a little pale-purple or green fluorite and in one case, 
on the western bluff, tabular crystals of barite. The croppings are said to contain 
gold values of low grade. It is by no means certain that these veins are of the 
same age as those of Cripple Creek. They may possibly be considerably older. 


INDEX. 


. A. Page. 

Abe Lincoln mine, description of. 147,276-279 

drainage of. 279 

gas in. 262 

geology of. 276-277 

history of. ’ 276 

location of. 5,147,272,276 

metamorphism in. 192 

minerals in. 121,192,195 

ores in. 174,210,278 

oxidation in.,. 198 

production of.*1. 276 

rocks in. 25 

Section through Stratton’s Independence mine and. 148 

veins of, character of. 156,158,165,177,195,277-278 

wpter level in. 241,279 

change in, figure showing. 242 

workings of. 276 

Abe Lincoln vein, character of. 277-278 

Acacia Gold Mining Company, mines of. 398-399 

Accident mine, description of. 306-308 

minerals in. 122 

ore from. 171,307-308 

rocks in. 306-307 

veins in. 307-308 

workings of. 306 

Acetylene lamp, air test by. 253 

Acknowledgments to those aiding. 14-15,41,233 

Actinolite, occurrence of. 50 

Addie C. shaft, location and description of. 271 

Adularia, occurrence of. 4,176,184,187.188,189, 

190,191,192,193,194,195,282,337,470,339-341 

JEgirine, occurrence of. 63,67,81,103,114,128 

.Egirine-augite, occurrence of. 63,103> 

Aileen claim, location of. 314 

Air, composition of. 252 

tests of. 253 

Ajax Gold Mining Company, mine of. 478 

Ajax mine, description of. 478-484 

dikes in. 91,92,95,480-481 

geology of. 479-481 

location of. 5,150 

minerals in. 120,128,174,185 

ore of. 194,208,213,462,470,481-484 

analyses of. 172,194,483 

plan showing location of. 213 

rock from, analyses of. 194 

shaft of, section through, figure showing. 479 

veins in. 157, 

158,159,162,164,478-479,481-483 

figure showing. 162 

water level in. 240,242 

workings of. 478 


Page. 

Albany tunnel, location and description of.. .*. 366 

minerals in. 128 

Albite, description of. 127 

occurrence of. 51,52,53,73,81,95,103,114,183 

Aldrich, Sherwood, data from. 242 

Alkalies, presence of, in vein-forming water.,. 222-223 

Allen, E. T., analysis by. 170 

Altaite, description of. 116 

Alteration, processes of. 184-204 

processes of, synopsis of. 7 

See also Metasomatism; Hydrometamorphism; 

Oxidation. 

Altman, mines near. 5,387,429 

rocks in. 84,91 

Alunite, description of. 125 

occurrence of. 4,114,170,199,200,377,379 

American Eagle mine, metasomatism in. 190 

water level in. 240,244 

change in, figure showing. 242 

workings of. 29,151,244,380-382 

Amphibole, description of. 63-64,128 

occurrence of... 185 

Anaconda, mines in and near. 5,308,321,330 

Anaconda dike, minerals in. 123 

Anaconda Gold Mining Company, mine of. 308 

Anaconda mine, description of. 308-313 

dip in. 150 

gas in. 313 

geology of. 309 

location of. 5,148 

minerals in. 122 

ore of. 210,311-312 

production of. 148,308 

rocks in. 26,34. 

analysis of. 79 

structure of, plate showing..'. 166 

tunnel in. 291 

veins of.. 158,161,162,165,309-312 

section of, figure showing. 161 

water level in. 312 

change in, figure showing. 242 

workings of. 308 

plan showing. 310 

Anaconda-Raven tunnel, location of.. 315,332 

minerals in. 126 

Anaconda vein, location and description of. 309,311 

Anaconda Mining and Milling Company, mine of. 308 

Anaconda Mining Company, mine of. 308 

Analcite, description of. 127 

occurrence of. 62-63,65,67, 

72-73,74,81,83,85,86,88,92,95,103,114 

Anchor claims, location of. 291,297 

Anchoria-Leland mine, description of. 291-297 


497 







































































































498 


INDEX 


Page. 

Anehoria-Leland mine, geology of. 293 

history of. 292 

location of. 5,148,291 

minerals in. 116 

ore of. 294-297 

production of. 148,292 

veins of. 157,165,294 

sections of, figure showing. 295 

water level in. 241,297 

change in, figure showing. 242 

workings in. 292-293 

plan showing. 295 


Anehoria-Leland Mining and Milling Company, mines 


of... 291-292,298 

Andesite, discussion of. 20 

occurrence of...,. 1,2,19 

Ankerite, occurrence of. 273 

Anna Lee dike, location and description of.. 439,440 

Anna Lee mine, chimney of. 447-448 

chimney of, stereogram of.. 447 

dikes in. 36,93,439,448 

minerals in. 121 

workings of. 433,437 

Anna shaft, location of. 426 

Anna spur vein, character of. 429 

Anorthite, description of. 127 

occurrence of. 81,114 

Anorthosite, description of. 55 

occurrence of. 20 

Antimony, occurrence of. 225 

value of. 170 

Apatite, description of. 126 

occurrence of. 49,52,54,55,64, 

67,74,76,78,81,83,86,88,93,103,114.193,194,340,474 

Apex claim, location of. 478 

Apex dike, location of. 480 

Apex vein, figure showing. 162 

location and description of. 158,159,164,478 

Appie Ellen claim, location of. 331 

workings of. 96 

Arapahoe claim, location and description of. 288 

Arcadia shaft, location and description of. 276 

Arcadia shoot, location and description of. 279 

Arequa, mines at. 358 

Arequa Gulch, placers in. 152 

prospects in. 150 

rocks in. 33 

Arfvedsonite, occurrence of. 114 

Argali, Philip, on Moose mine. 343 

Arsenopyiite, description of. 122 

occurrence of. 169 

Augite, occurrence of. 67,81,83,92,93,103,114 

August Flower claim, location of. 330 

Australia tunnel, rocks in. 350,354 

Aztec shaft, breccia contact in. 30 


B. 


Barite, occurrence of. 

B,aryta, occurrence of. 

Basalt, occurrence of. 

See also Dikes, basic. 

Basalt vein, location and description 

Basement rocks, character of. 

Battle Mountain, location of. 

minerals in. 

mines on. 

production of. 

view of. 


4,114,124,174,175,182 
. 220 


of. 382 

. 19-20 

. 430 

. 123 

. 5,430-496 

. 135 

. 34 


Page. 

Battle Mountain, mines on, workings of, plan showing 26 

rocks on. 21,32,33,57,70,78,83-84,430 

Battle Mountain tunnel, location of. 478 

Bayard Mining and Lease Company. 369 

Beacon claim, location of. 358 

Beacon Hill, drainage of. 9,235,251 

drainage of, figure showing. 250 

mines on. 5,148,349-361, 496, 

production of. 135 

view of. 350 

phonolite plug of. 34,349,354 

rocks of. 34,57,349,496 

section across, figure showing. 351 

structure of. 2 

view of. 350 

Beacon Hill mine, oxidation in. 198 

Beaver Creek, placers on. 152 

Becker, G. F., on deposition. 229 

Bennet and Myers, ranch of. 130 

Bernard Creek, prospects on. 151,280 

Bertha B. claim, location of. 341 

workings of. 342 

minerals in. 126 

Bibliography of district. 15-17 

Big Bull Mountain, mines of. 495 

rocks of. 29,34,70,97,495 

view of. 34 

Big Twenty Mining Company, development by. 496 

Biotite, description of. 128 

occurrence of. 44. 46,49,50,52,56,64,73-74,77,78,85,86, 

89,92,95,96,100,103,114,175,193,194,436 

Biotite-feldspar, vein of. 183 

Biotite trachyte, abundancy of. Ill 

analysis of. 104 

area covered by. 110 

See also Latite-phonolite. 

Black Diamond mine, location of. 477 

production of. 151 

Black Diamond vein, character of. 453 

Black vein. See Work vein. 

Block 7 mine, production of. 386 

Block 8 mine, description of. 384 

dikes of. 36,91,95,98,384-385 

ore of. 385 

rock of. 384 

analysis of. 96 

workings of. 384 

Block 10 mine, location and description of. 386 

Blue Bell tunnel, drainage by. 234,235 

Blue Bell vein, minerals in. 121 

Blue Bird Gold Mining and Milling Company,mine of. 372 

Blue Bird mine, dikes in. 91 

gas in. 261 

location of. 5,149,372 

minerals in. 116,120,121,122,176,182,372-373 

ore of. 171,205,372-373 

oxidation in. 203 

production of. 372 

rocks in. 33 

silver in. 203,372 

veins of, character of. 163,173,177,179,203,372-373 

section of, figure showing. 163 

structure of, figure showing. 163 

water level in. 240,245 

change in, figure showing. 242 

Blue Bird vein, location and description of. 163, 

173,203,371-373 

Blue Hill, mines on. 5 
































































































































INDEX. 


499 


Page. 

Bobtail mine, opening of. 433 

Bobtail veins, location and description of. 159, 

103,104,105,107,179, 433, 439,440,440-447, 
452-453,450, 400-404,471-472, 474, 478-479 

Bogart mine, location and description of. 365 

Bolivar claim, location and description of. 283 

Bonanza King vein, location and description of. 174, 

192,200,200,298,302-304 


Breccia, alteration of. 184,191-192 

character of. 30-31,97-100 

description of. 19,30-32,97-9S, 191 

extent of. 25-30,110 

fissures in. 159 

formation of. 24-25,32,38 

granite and, contact of.25-30 

intrusions in. 32-30 

occurrence of. 19-21,25-30, 35, 97, passim 271-495 

ores in. 146 

origin of. 56 

oxidation of. 197 

Brind Mountain, prospects on. 150,495 

rocks on.■. 50,495 

section through, figure showing. 37 

Browne, A. W., analysis by. 255 

Bruce, J., work of.'. 14 

Brunton, D. W., on mine drainage. 250-251 

Bryan Fraction claim, location of. 349 

Buena Vista incline, location of. 389-390 

Buena Vista vein, character oi. 123, 

156,157,158,103,160,179,212,387,389-392,395 

projection of, figure showing. 390 

section of, figure showing. 390 

Buffalo and Cripple Creek Gold Mining Company, mine 

of. 490 

Bull Cliff, drainage of. 245 

rocks of.; 21,30,70,83,88,198,381,383 

view of. 362 

Bull Cliff trachydolerite. See Trachydolerite. 

Bull Hill, drainage of. 244-245 

location of. 362 

mines on.*. 149,302 

production of. 135 

rocks of. 29,32,70,91,93,98,198,302,3S3 

south slope of, view of. 362 

veins on. 302 

views from. 280 

water level at. " 

Burke and Fry shaft, location of. 322 

Burns, James, location by. i . 430 

Burns dike, location of. 399 

Burns mine, description of. 398 

production of. 398 

veins of. 149,398 

Burns shaft, character of. 431,449 

section of, figure showing. 434 


i 




Calaverite, analyses of. n7 

composition of. 169 

description of. 117-118,169 

occurrence of. 4, 6, 114-118, passiiji 169-487 

See also Tellurides. 

Calcite, description of... 124 

occurrence of. 4,114, 

169,174,186,187,188,190,191,192,194,337,343,443 

Calcium, presence of, in vein-forming water.,. 222 

Caledonia mine, description of. 313 

Calf Mountain, rocks of. 43,48,50 


Page. 

Cameron, location of. 281 

mines and prospects near. 281,383-386 

rocks near. 30,281 

Campbell vein, character of. 391,392,393,417,421 

Capitalization, abuses of. 144-145 

Captain veins, location and description of. 154 

157,159,162,177,205,434,437-445,448 

face of, figure showing. 162 

Carbonate Hill, prospects on. 151,271 

rocks on. 271 

Carbonate Queen mine, description of. 495 

veins of..T. 494,495 

Carbonates, description of. 122-129 

'presence of, in vem-forming waters. 221 

Carbon dioxide, danger from. 253 

occurrence of. 252,258-259 

Cardinal mine, description of. 313 

Cardinal vein, character of. 164 

Carr vein, location of. 427 

Cashen fault, location and description of_ 166-167,489-491 

Cashen vein, character and description of. 489,493 

Catherine dike, location of. 336 

Celestite, description of. 124-125,220 

occurrence of. 4,6,114,169,174,175,182,220,286,287,340,341 

vein of. 183 

Chalcanthite, description of. 126 

occurrence of. 4,114 

Chalcedony, description of. 123 

occurrence of. 4,100.114,169,174,176,178,190,200 

Chalcocite, description of. 122 

occurrence of. 114,169 

Chalcopyrite, description of. 121 

occurrence of. 114,169,174,353 

Champion claim, location of. 478 

Chance claim, location of. 291 

Chance vein, location and description of. 162,166,292-297 

section of, figure showing. 295 

Chasm, formation of. 24 

See also Volcanic eruptions. 

Cheyenne vein, character of.. 164,170,188,206,209,389,391,392 

projection of, figure showing. 390 

Chicago and Cripple Creek tunnel, minerals in. 121,126 

Chicago tunnel, breccia in. 25,197 

location and description of. 277,285 

Chicken Hawk claim, location of. 330 

Chief shaft, location of. 315 

Chlorides, occurrence and source of. 219-220 

Chlorination, employment and cost of. 4-5,139-140 

plants for, location of. 139 

process of. 140-142 

Chlorite, description of. 128 

occurrence of. 114,128,188 

Chloropal, description of. 128 

occurrence of. 114,128,200 

Christmas mine, description of. 422-424 

veins of. 423-424 

workings in.:. 408,422 

Christmas shaft, section through, figure showing. 423 

Chrysocolla, description of. 129 

occurrence of. 114,286 

Cinnabar, description of. 121 

occurrence of. 114 

City View claim, location of. 291 

City View dike, location of. 166,293,294 

City View vein, location and description of. 292-294,297 

C. K. & N. mine, description of. 355-358 

gas in. 262,358 

geology of. 356 


* 






























































































































500 


INDEX 


Page. 

C. K. & N. mine, location of. 5,148,355 

metasomatism in. 188 

minerals in. 118,120,121,125,175 

ore of. 174,177,356-357 

production of. 355 

water in. 358 

veins of, character of. 159,162,181-182,355-358 

structure of, figure showing. 181 

view of. 350 

workings of. 355 

C. K. & N. Mining Company, mines of. 355 

C. K. & N. vein, location and description of. 159, 

162,181-182,351-358 

minerals in, character of. 159,162,166,174,176,177,178 

Clyde mine, water level in. 240,242 

Coal, analyses of. 31 

occurrence of. 31,114,129,317,319 

evidence from. 31,38 

Cobb vein, location and description of... 159,164,206,302,304 

Cocking, Henry, development by. 130 

C. O. D. mine, description of. 272 

history of. 272 

location of. 5,104,272 

minerals in. 122,200,272 

ore from, analysis of. 117 

ore bodies in. 207 

oxidation in. 198,200 

production of. 148 

prospects near. 272-273 

rocks in. 29 

veins in... 206,272 

workings of, description of. 272 

Coin vein, location and description of. 164, 

166-167,485,488-492 

Colloid solutions, diffusion of. 230-231 

Colorado, cooperation with. 1,11 

Colorado Boss claim, location and description of.... 287,330 

Colorado Boss vein, character of. 309-310 

Colorado City mine, workings of. 433,437,442 

Coloradoite, description of... 115 

Colorado Springs, reduction plants at. 139 

temperature at. 269 

Columbia claim, location and description of. 349,350 

Columbine tunnel, location of... 488 

Columbus claim, location of. 349 

Combination claim, location of.... 374 

Comet incline, location of. 391 

Contact vein, character of. 160 

Conundrum mine, description of. 297-305 

dikes in..■. 36,301,362 

gas in. 254-255,250-257,258,262-208 

analyses of... 255,263,264 

geology of. 300-301 

location of. 5,146,298 

minerals in. 121,174,193 

ore of.!. 171,302-305 

production of. 148 

relations of Midget mine and, figure showing. 300 

rocks in. 25 

temperatures In. 270 

vein in. 302,304-305 

plate showing. 160 

ventilation of, figure showing. 263 

view of. 18 

water in. 305 

workings in, plan showing.,. 299 

Conundrum vein, location and description of. 165, 

298,302-305 


Page. 

Copper, description of. H5 

occurrence of. 114,171,172,225,307,372,402,414 

value of. 170 

Copper Mountain, rocks on. 22,30,34,57,97,98 

Copper Mountain mine, location and description of— 280 

Cottontail claim, location of. 291 

Countryman and Jaquith, on El Paso tunnel. 237 

Cow Mountain, prospects on. 151,283 

rocks of.:. 58 

Creede, mine gas at. 259-260 

mine gas at, analysis of. 260 

Creston Big Eight Mining Company, mine of. 274 

Creswick, Victoria, gas in mines at. 259 

gas in mines at, analysis of. 259 

Cripple Creek, lower part of, rocks and mines on. 496 

Cripple Creek (P. O.), elevations in. 12,13-14 

history of. 132 

mines at and near. See Mines. 

placers in and near. 152 

reduction plants at. 139 

temperature at. 269 

views of. 18 

Cripple Creek and Gold Hill tunnel, location and de¬ 
scription of. 291,292 

rocks in..*. 293 

Cripple Creek granite, analysis of. 101-102 

description of. 3,23-24,45-46 

occurrence of. 20,23,29,314 

petrology of. 46-47 

Cripple Creek Homestake Mining and Reduction Com¬ 
pany, property of. 285-286 

Cripple Creek volcano. See Volcano; Volcanic effects; 
Volcanic cone. 

Cross, Whitman, on breccia. 20-21,22 

on Cripple Creek geology, summary of. 18-19 

on crystalline rocks. 3,43 

on High Park lake beds.’. 22 

on igneous rocks. 1-2,18-19,21,56 

on metasomatism. 195,196 

on schists. 52 

work of. 1,11, IS, 41-42 

Cross veins, location and description of. 472,474,475 

Crystalline rocks (prevolcanic), description and petrol¬ 
ogy of. 42-56 

mineralization in. 24 ' 

occurrence and character of. 23-24 

Crystallization, products of.:. 101 

Cumberland claim, location of. 298 

Cyanide process, description of. 140 

employment and cost of. 4-5,139-140 

plants for, location of. 139 

D. 

Damon mine, description of. 289-290 

dipin. 156 

location of. 149,289 

ore of. 210,290 

production of. 289 

rocks in. 289 

veins in. 289-290 

figure showing. 210 

workings in. 289 

figure showing. 210 

Damon vein, location.and description of. 290 

Dante Gold Mining Company, mine of. 370 

Dante mine, description of. 370-372 

dikes in. 371,372,38i 





























































































































INDEX 


501 


Dante mine, ore in. 

rocks in. 

veins in. 

figure showing. 

workings of. 

Dante vein, character of. 

Dead Pine mine, description of 
dikes in. 


Page 

. 211,371-372 

. 33 

. 158,100,371-372 

.210,371 

. 370-371 

. 362 

.. 484-487 

35,473,477,480,485-486 


geology of. 

location of. 

ore of. 

plan showing. 

rocks in. 

veins in. 

workings of. 

Dead Pine vein, location and character of 
Dead vein, location and description of... 

Deadwood mine, description of. 

geology of. 

minerals in. 

ore of. 

production of. 

rocks in. 

veins of. 

Deadwood No. 2 mine, description of_ 

dikes in.. 

geology of.. 

ores of. e .. 

production of.. 

veins of.. 

Deerhorn mine, description of. 

gypsum in. 

.minerals in. 

ores of.. 

oxidation in. 

workings of.. 

De la Vergne, E. M., development by_ 

Delmonico mine, description of. 

Deposition, depth of.. 

mode of. 

time of.. 

Dexter Gold Mining Company, mine of. 

Dexter mine, description of. 

location of. 

ore bodies in. 

veins in. 

workings of. 

Diabase, description of. 

occurrence of... 


. 485-486 

. 5,150,484 

... 207,213,486-487 

. 212 

.27,33 

159,165,485,486-487 

. 484-485 

. 485,486 

. 26,166,333 

. 404-405 

. 404 

. 129 ! 

.212,405 

. 404 

. 33,404 

. 405 

. 406-408 ! 

... 393,406-407,408 j 

. 406 

. 407 

. 406 

. 406-408 

.. 284-285 

. 284-285 

. 121,125,201 

.. 284 

. 197 

. 284 

. 4,131 

.. 408 

.. 226 

. 228-231 I 

.. 226-227 

. 373 

. 373-374 

. 373 


373-374 
. 373 

56 i 
. 24,56 


petrology of. 56- 

Diallage, occurrence of. 54,55,56,114 

Diamond mine, workings of. 433 

Diamond vein, location and description of. 157, 

159,162,165,435,439, 440,445-446,452-453,462,470 

Dikes, basic, alteration of. 184,192-193 

area of.35-36,159,167 

character of.... 35-36,159 

convergence of. 155 

description of. 90-91,97 

fissures along. 165 

occurrence of. 35-36,167, passim 271-495 

types of. 91' 

descriptions of. 91-96 

view of. 396 


Dikes, diabase. See Diabase. 

Dikes, granite, occurrence of. 277 

See also Granite. 


■Page. 

Dikes, latite-phonolite, occurrence of. 271,273,373,384-385,412 
See also Latite-phonolite. 

Dikes, phonolite, alteration of. 184 

character of. 164 

Assuring in. 164 

importance of. 35 

mineralization of. 446 

occurrence of. 35,38, passim 271-496 

See also Phonolite. 

Dikes, trachydolerite, occurrence of. 323-324,387 

See also Trachydolerite. 

Dillon mine, description of. 476-477 

dikes in. 473,476,477 

geology of. 477 

location of. 150,476 

minerals in. 121 

ore of. 213,477 

veins in.:. 158,477 

workings of. 477 

Doctor claim, location of. 314 

workings on. 315 

Doctor-Jackpot Company, mines of. 314 

Doctor-Jackpot group, location of. 314 

view of. 292 

Doctor-Jackpot mine, coal in.31,317 

coal in, analysis of. 31 

description of.317-321 

gas in. 261 

geology of. 317 

history of.314-315 

location of,. 5,148 

minerals in. 115,121,122,175 

ore of. 171,318-321 

oxidation in.,... 198 

production of. 148,314 

veins in. 157,161,162,163^ 164,179,316-318,319-321 

workings of. 315,317 

plan showing. 316 

Doctor-Jackpot- veins, location and description of. 317, 

318-320 

Doctor vein, character of.318,319-320 

oxidation of. 198 

Dolly Varden mine, dikes in.36,91 

minerals in. 122,175,183 

Dolomite, occurrence of. 4,6,98,114,124,169-176,181-195, 

281,318-320,328-329,340-343,376-379,410,428,443,484 

Dorcas mill, cyanide process at, description of. 140 

Dorothy vein, character of. 154,158,199,489,490,491 

Doveton, G. D., on ore composition. 173 

Doyle, James, location of mine by. 430 

Drainage, character of. 40 

Drainage, mine, methods of. 9-10,133,235-238,239-251 

methods of, figures showing. 236,242 

See also Tunnels; Water, underground; Water 
level. 

Drainage tunnels. See Tunnels, drainage; Drainage, 
mine. 

Drury vein, character of. 456,463 


E. 


Eakins, L. G., analysis by. 66 

East Bobtail vein, character of.... 456,460 

East Drury vein, character of. 456 

East Emerson vein, character of. 456 

East Independence vein, character of. 456 

East London vein, character of. 456 


I 





























































































































502 


INDEX. 


Page. 

East veins, location and description of. 371, 

392,393,452-453,456,462,463,471,474 

section of, figure showing. 390 

East Victor vein, location and description of. 388,392 

East-West dike, location and description of. 485,486 

Eclipse mine, gas in. 260 

water level in. 240,244 

change in, figure showing. 242 

Economic mill, process in, description of. 142 

Edwards shaft, character of. 394 

E. F. C. prospect, location and description of. 282 

Elevations, data on. 12-13,147 

Elizabeth Cooper claim, location of. 314 

workings on.315,317 

Elkhorn mine, location and character of. 271 

production of. 151 

Elkton Consolidated Mining and Milling Company, 

mines of. 331 

Elkton mine, description of. 331-341 

dikes in. 335-336 

plan showing. 332 

drainage of. 10,237-238,242-244 

fissures in, plan showing. 332 

gas in. 254-255,260 

analysis of. 255 

geology of. 333-336 

history of. 331 

location of. 5,148 

metasomatism in. 193 

minerals in. 116,120,126,175,177,181 

ore of. 206,209,211,213,336-341,462 

plan of. 338 

production of. . . 148,331 

rocks in.'....26,30 

section of, figure showing. 333 

tree trunk in. * . 31 

valuation of. 144 

veins of, cavity in, figure showing. 178 

character of.. 157,164,166,174,177-178,332-333,336-339 

section of, figure showing. 178 

view of. 332 

water level in. 240,341 

change in. 237-238,242-244,248,249 

figure showing. 242 

relation of El Paso tunnel and, figure showing.. 236 

workings of. 151,331-332 

Elkton-Raven mine, dikes in..-. 36 

El Paso Consolidated Gold Mining Comoany, mines of. 349 

El Paso dike, description of. 159,350 

location of, figure showing. 350 

water behind.,. 249 

El Paso Gold King mine. See Gold King mine. 

El Paso mine, description of. 349-354 

dikes in. 159 

flooding of. 249 

gas in. 254,262 

geology of. 350-351 

history of. 349 

location of. 5,148,349 

minerals in. 115,118,120,121,122,124,175,176,177,178 

ore of. 170-171,203,209,353-354 

analyses of. 173 

production of. 349 

rocks in. 34 

sorting at. 137 

veins of, character of. 159,165,166,235,351-353 

section of, figure showing. 209 

view of. 350 


Page. 


El Paso mine, water level in. 241 

water level in, change in. 249 

figure showing. 242 

workings of. 151,349-351 

plan showing. 350 

section of, figure showing. 351 

El Paso tunnel, drainage by. 4, 


9-10,133,235-238,243,245,246,249,329 


gas in.:. 262 

relation of, to water level in Elkton mine, diagram 

showing. 236 

El Paso vein, location and description of. 159, 

165,166,235,351-352,353-354 

section of, figure showing. 209 

Emerson vein, location and description of. 158, 

159,165,452-453,462-463, 464 


Emma vein. See Empire vein. 

Emmonsite, analysis of. 119 

description of. 118-119 

occurrence of. 4,114,289,343 

Empire No. 2 vein, location and description of. 164, 


166,212,393-395 


production of. 394 

workings on. 394 

Empire State Gold Mining Company, mine of. 395 

Empire State mine, ore from, photomicrograph of.... 186 

production of.*. 395 

veins of. 149,393-395,396 

workings of. 396 

English companies, misfortunes of. 145 

Enrichment, secondary, description of. 204 

Epidote, occurrence of. 55,72,73,86,185,192 

E. Porter Gold King mine, description of.3(fe-306 

rocks in. 34 

veins in. 294,306 

Epsomite, description of. 126 

occurrence of. 4,114 

origin of.,. 201 

Erosion, effects of. 36,38,39-40 

Eureka claim, location of. 358 

Evans, R. T., work of. 11 

Excelsior vein, location and description of. 309,312 


F. 


Fannie B. claim, location of. 349 

Faulting, occurrence of. 165-167 

Fault vein, character of. 165-166,294 

figure showing. 293 

, location of. 294 

Favorite mine, dike in. 381 

production of. 380 

vein of. 382 

Feldspar, occurrence of. 59,72-73,89,169 

Femay, William, development at. 131 

Field work, extent of. 1 

Financial conditions, statement of. 5,143-146 

; Findley Gold Mining Company, mine of. 409 

Findley mine, description of. 409-412 

gas in. 260 

geology in. 156, 409 

location of. 5,408, 409 

minerals in. 120,175,176 


ore in. 

production of.. 

rocks in.. 

section of, figure showing 

veins of. 

figure showing. 


.212,213,411-412 

. 409 

. 33,34,381 

. 410 

163,166,179,383,410-411,424 
. 410 





























































































































INDEX 


T 


503 


i 


Page. 

Findley mine, veins of, section of, figure showing. 410 

water level in. 240,245,246 

change in, figure showing. 242 

workings of. 408,409 

Findley vein, location and description of. 410 

Finlay, J. R., on Cripple Creek ores. 137 

Fissures. See Lode fissures. 

Flats, description of. 210 

Flat vein, location and description of_ 452,456,462,463-464 

Florence, reduction plants at. 139 

Fluorides, occurrence and derivation of. 218-219 

Fluorine, occurrence of. 190 

origin of. 218-219 

presence of, in vein-forming water. 218-219 

Fluorine mine, description of. 280 

gas in. 269 

location of. 151,280 

minerals in. 121,174 

production of. 280 

rocks in. 30,280 

Fluorite, occurrence of. 3,4,6,47,100,114,122 

passim. 160-493 

Fluorite vein, location and description of. 211,373-374 

Fort Pitt Mining Company, mine of. 281 

Fountain formation, occurrence of. 22 

Fox vein, location and description of. 368,371-372 

Free Coinage Gold Mining Company, mines of... 396,402,403 

Friday mine, production of. 151 

Friday shaft, location and description of. 287 

Frisbee, T. F., development by. 4,131 

G. 

Gabbro, character of. 3 

occu rrence of. 3,55 

Galena, deposition of. 225 

description of. 121 

occurrence of. 4,6,7,114,121, 

169,174-178,184,188,192-194,273,278,280-281,289, 
303-308,311,353,375,414,418,422,428, 443, 464, 495 

oxidation of. 200 

Galena Hill, mines on. 281 

Galena mine, location of. 151,280 

minerals in. 120,178 

production of. 281 

veins of. 281 i 

workings of. 280-281 

Galeta vein, location and description of. 317 

Garfield shaft, rocks in. 382 

Gases, mine, analyses of. 255,259,260 

composition of. 252,254-255 

danger from.- - - 10,253,256 

distribution of. 253-254.260-269 

effects of. 256 

occurrence of. 10.253-254,256-257,258-269 

remedies for. 258 

source of. 10,257-258 

See also particular mines. 

Gee Mima claim, location of. 478 

Geneva mine, description of. 291-292 

location of. 292 

production of. 292 

workings in. 292 

plan showing. 296 

Geological map, of district.. Pocket. 

of district, description of. 18,19 

of Portland mine.. 434 

Geology, account of. 1-2,18-40 

See also particular mines. 


Page. 

Giilett, location of. 281 

mines and prospects near. 281,282-283 

view of. 280 

Gleason shaft, location of. 366 

Globe Hill, geology of. 283-287 

minerals in. 124 

mines on. 5,148,158,284 

oxidation at. 197 

depth of. 7,197 

rocks on. 147,283 

Globe mine, location of. 148 

Globe tunnel, location and description of. 284 

Glockerite, description of. 125 

occurrence of. 114 

Glorietta shaft, location and description of. 412,413,415 

Gneiss, alteration of. 184 

description of. 3,19,48-49 

occurrence of. 1, 

20,23,48,50,271,276-278,291,298,300-301,303-305 

petrology of. 49-50 

types of. 48,50 

Gold, deposition of. 229 

description of. 114-115 

occurrence of. 4,6,114,169 

presence of, in vein-forming water. 223-225 

production of.4,134-135 

See also Tellurides; Calaverite; Sylvanite. 

Gold Bond mine, dike at. 91,92 

Gold Coin mine, description of. 487-494 

dikes in. 35,480,490 

drainage of. 238 

geology of. 490-491 

location of. 5,150 

mill of. 487,488 

minerals in. 121,123 

ore in. 199,207,208,214.491-493 

production of. 150 

veins of, character of. 154,156, 

158,159,161,163,164,168,174.178,179,207,488-493 

view of. 34 

water level in..". 197,234,240,494 

change in. 238,494 

figure showing. 242 

workings in. 151.487.488 

plan showing. 488 

Gold Coin Mining and Leasing Company, mine of.• 487 

Gold deposits, characteristics of. 153 

development of, history off. 4-5,130-134 

distribution of. 5,140,146,147 

enrichment of. 203.204 

mining and milling of.4-5,138-142 

occurrence of, mode of.6,153-168 

oxidation of. 203 

production of. 4,134,135 

structure of. 6,153-168 

tenor of. 6-7 

types of. 6,153 

See also Ores; Ore deposits; Ore shoots; Veins; 

Lode fissures; etc. 

Gold Dollar mine, geology of. 359 

location of. 5,148,358 

minerals in. 118 

ore in. 360-361 

rocks in. 34-35,359 

veins in. 360-361 

workings in. 358 

plan showing. 359 


« 

































































































































504 


INDEX. 


Page. 

Gold Dollar vein, location and description of. 360 

Golden Cycle mine, description of. 424-429 

gas in. 260,426 

geology of. 426-427 

location of. 5,408,425-426 

metasomatism in. 190,191-192 

minerals in. 182,191 

ore of.•.. 172,212-213,428-429 

analyses of. 172 

oxidation in.i. - 198,428 

production of. 149-426 

rocks in. 29,32-33,190 

analysis of. 192 

veins of. 156,160,161,424,427-428 

structure of. 428-429 

figures showing. 160 

view of. 416 

workings in.. 408,426 

figure showing. 428 

water level in..*.. 240,245.246 

change in, figure showing. 242 

Golden Cycle Mining Company, mine of. 424 

Golden Discovery claim, location of. 487 

Goldfield, mines near. 5,387-429 

view of. 34,416 

drainage of. 9,235,244 

location of. 291 

Gold Hill, mines on, description of. 5,148,287,291-313 

mines on, production of. 135 

north slope of, view of. 292 

oxidation on. 198 

rocks on. 25-26,32,34,70,147,291 

view from.. 18 

workings in. 291 

Gold King dike, location and description of. 274-275,277 

Gold King Gold Mining Company, mine of. 273 

Gold King mine, description of. 273-274 

drainage of. 273 

history of. 131,148,273 

location of. 5,148,272,273 

minerals in. 116,126 

ores of. 273-274 

oxidation in. 198 

production of. 273 

veins of. 273 

water level in. 240,273 

• change in, figure showing. 242 

workings of. 273 

Gold King vein, character of?. 272 

Gold Knob shaft, location and description of. 426 

Gold Pass claim, location of. 292 

Gold Pass dike, location and description of.. 275-276,277,278 

Gold Run, prospects on. 150 

Gold Sovereign mine, description of. 367-369 

dike in. 95,368 

location of. 367 

metasomatism in. 190 

minerals in. 120 

ore of. 211,368-369 

photomicrograph of. 186 

oxidation in. 198 

production of. 367 

rocks in. 33 

veins of. 367-368 

Gold Sovereign Mining and Tunnel Company, mines of. 367 

Gold Sovereign vein, character of. 362 

Gold Watch vein, location and description of.. 496 


Page. 

Goodwill tunnel, location and description of. 291,292 

rocks in. 25,293 

Gortner, M. C., mine of. 274 

Grafton Gold Mining Company, mine of. 286 

Granfield, Horace, mine of. 355 

Granite, age of. 47-48 

alteration of. 184,192,193-195 

analyses of. 45,101-102,196,483 

breccia and, contact of. 25-30 

breccia of. 99 

description of... 1,3,43,45-46,47 

divisions of. 3,43 

occurrence of. 1, passim 276-496 

intiusions on. 24,35 

occurrence of. 1, passim 276-496 

ore bodies in, figures showing. 213,338 

petrology of. 43-45,46-47 

See also Pikes Peak granite; Cripple Creek granite; Spring 

Creek granite. 

Granite Gold Mining Company, mine of. 471 

Granite mine, description of. 471-475 

dikes in.. 34,95,473,477 

geology of. 472-473 

location of. 5,150,471 

ore of. ; . 213,473-475 

production of. 471 

rocks in. 27,85 

veins in, character of.. 162,179,206,471-472,474-475 

water in. 475 

workings of..'.. 471 

Granite ore, analysis of. 172 

character of. 7,193-194,473-475 

deposition in. 229 

Occurrence of. 338-339,360-361,473 

Granite vein, location and description of. 471-472,474 

Grant, L. S., data from. 394 

Grant vein, location and description of. 158, 

165,452,456,462,463 

Graton, L. C., on description and petrology of meta- 

morphic and igneops rocks. 41-113 

work of. 14,18,20,22 

Great Westerh claim, location and description of. 283 

Gregory claim, location of. 331 

workings on. 332 

Grouse Hill, prospects on. 150,495-496 

rocks of. 19,22,34,37,38,57,495 

section through Straub Mountain and, figure 

showing. 37 

view of. 350 

Grouse shaft, rocks in. 382 

Guyot Hill, mines on. 330 

mines on, production of. 135 

Gypsum, description of. 125 

occurrence of. 4,114,197,284-285 

origin of. 201,220 

H. 

Half Moon mine, description of. 292,297 

history of. 292 

location of. 5,148 

production of. 148,292 

veins in. 297 

workings in, plan showing.!. 295 

Half Moon vein, location of. 275 

Hallett & Hamburg claim, location of. 478 

Hammond, J. H., advice of. 450 

Happy Thought mine, gas in. 259-260 
































































































































/ 


INDEX. 505 


• Page. 

Happy Year mine, location and description of. 365 

Harlan H. claim, location of. 292 

Harman, John, development by. 430 

Harrington vein, character of. 396,397 

Harrison & Sevier, mine of. 288 

Harrison vein, location and description of. 427,429 

Hawkeye shaft, location and description of.. 283,433,437,442 

Henry Adney mine, view of. 350 

Hessite, description of. 116 

Hidden Treasure veins, location and description of. .. 157, 

173,434,437,440,441,443,444,445,448 

High Park lake beds, correlation of. 2,22 

Hillebrand, W. F., analyses by. 45, 

66,79,119,170,172,173,189,194 

on celestite. 125 

on emmonsite. 119 

on tellurides. 224,356 

Hills, Fred, manual of mines by. 144 

Hills, V. G., on Amia Lee ore chimney. 447 

on underground water_ 12,233,239,246,321,449,460,470 

Hillside claim, copper on. 115 

Hobo claim, location of. 330 

Holden, Edward, chlorination plant of. 139 

Homestake mine, location of. 148 

veins in. . 158 

Hoosier mine, description of. 286-287 

location of. 286 

production of. 152,286 

veins in, character of. 206,286 

workings of. 286 

Hoosier vein, character of. 287 

Hornblende, occurrence of ... 73-74,81,83,85,86,92,93,103,114 

Houghton, Richard, gold found by. 131 

Howard flat vein, location and description of. 156, 

161,163,1?7,179,182,210,309,312,324 

section of, figure showing. 161 

temperature on.,. 269 

Hiibnerite, description of. 127 

occurrence of. 4,114,169,174 

Hull City, placers at. 152 

Hull City mine, description of. 412-415 

gasm. 253,260 

geology of. 412 

location of. 5,408,412 

minerals in. 122 

ore of.. 170,213,413-415 

oxidation in. 198 

production of.-.. 149,412 

rocks in. 34,412 

section ot figure showing. 414 

veins in. 158,159,253,254,413,413,424 

water level in, change in, figure showing. 242. 

workings in. 412 

map showing. 413 

Hull City Placer mine, water level in. 234,240,245,246 

water level in, change in, figure showing. 242 

Humboldt prospect, location and description of. 287 

minerals on. 125 

Hydrocarbons, presence of, in vein-forming water. 221 

Hydrogen sulphide, presence of, in vein-forming water. 222 

Hydrometamorphism, alteration due to. 184 

evidence of. 196 

process of. 185 

See also Metasomatism; Alteration; Oxidation. 

I. 

Ida B. claim, location of. 314 

Ida May mine, description of. 347-348 


Page. 

Ida May mine, minerals in. 129 

ore of. 211,348 

prod uction of. 347 

Iddingsite, occurrence of. 96,192 

Igneous rocks, character of. 1 

description of. 3 

divisions of. 101 

occurrence of. 1-2 

petrology of. 3,101-113 

See also Volcanic rocks. 

Ilsemanite, description of. 123-124 

occurrence of... 114 

Independence, mines near. 5 

rocks near. 32 

view of. 362 


Independence Consolidated Mining Company, mine of. 412 
Independence mine. See Stratton’s Independence 
mine. 

Independence dike, location and description of. 458,460 

Independence veins, location and description of. 159, 


160,164,206,440,452-453,456, 461-462,463,464 

Ingham claim, location of. 314 

workings on. 315,317 

Ingham vein, location and description of. 318,320-321 

Intermediate vein. See Cobb vein. 

International vein, location of. 304 

Intrusive rocks, occurrence of. 32-36 

See also Igneous rocks; Dikes; etc. 

Iron, presence of, in vein-forming water. 222 

Ironclad Hill, mines on. 285,288-290 

rocks on. 147,283 

Ironclad mine, geology of. 29,286,288 

location of. 148,285 

minerals in. 121,122,125,129,183 

oxidation in. 197 

production of. 285 

veins of. 286 

workings of. 286 

Iron Mountain, dike on. 102 

Iron Mountain Mining and Milling Company, mines of. 280 

Iron ocher, occurrence of. 285 

Iron vein, location of. 294 

Isabella dike, location and character of. 381,383,396-397 

Isabella lode system, location of. 387 

mines on. 387-393 

Isabella mine, description of. 389-393 

dike in. 390 

analysis of. '93 

gas in. 4 . 260 

geology of. 389 

location of. 5 

metasomatism in. 195 

minerals in. 121,122,188 

ore of. 170,206,209,213,391-393 

oxidation in. 198,391 

production of. 149,389 

rocks in.29,30,34 

veins of, character of. 156, 

159,164,166,206,212,387,390-392,393-395 

figures showing. 390 

map showing. 388 

water level in.. 197,198,234,240,245,246 

changes in, figure showing. 242 

workings of. 387,389 

Isabella Mines Company, mines of. 389 

Isabella trachydolerite, abundancy of. Ill 

analyses of. 93,104 

area covered by. 110 





























































































































506 


INDEX. 


Page. 


Isabella trachydolerite, composition of 

description of. 

occurrence of. 

petrology of.. 

Ithaca tunnel, location of. 


. 91-93 

. 91 

91,381,383,390,396-397 

. 91-92 

. 478 


J. 


Jack G. claim, location of. 314 

Jackpot claim, location of. 314 

shaft on. 315 

Jackpot vein, character of.166,318,319-320 

oxidation of. 163 

Jackson shaft, location and description of. 288, 

367-368,370-371 

Jaquith, A. C., on mine drainage. 10,248 

Jaquith and Countryman, on El Paso tunnel. 237 

Jaycox shaft location of. 305 

Jeff Davis mine, location and description of. 288 

Jefferson mine, description of. 292-295 

location of. 292 

production of. 292 

veins in. 294 

workings in. 292 j 

plan showing. 295 

Jefferson Mining Company, mine of—. 292 

Jennie Sample mine, dike in. 93 

rocks of, analysis of. 95 

Jerry Johnson mine, location of. * 149 

ore bodies in. 210 

production of. 288 

veins in. 166,288 

workings of. 288 

Jerry Johnson Mining Company, mine of. 288 

Jerry Johnson vein, character of. 288 

Joe Dandy mine, description of. 345 

veins in, character of. 206,345 

John A. Logan mine, coal in. 31 

dike in. 372,381 

gas in. 261,380 

location of. 5,149 

rocks in. 32 

water level in. 240,244 

change in, figure showing. 242 j 

workings in. 380 

Johnson, Fred, data from. 261 

J oily Tar claim, location of. 478 

June Blizzard claim, location of. 478 


Kalagoorlite, description of. 116 

Kaolin, description of. 128-129 

occurrence of. 72,86,114,128,170,199,282,283, 

285,287,347,366,369,, 372,374,391,398,400 


origin of. 170,201 

Katinka mine, description of. 330 

minerals in. 120 

Kentucky Belle claim, location of.. 341 

Kentucky Bill claim, location of. 331 

Keystone vein, character of. 307,308 

King shaft. See Glorietta shaft. 

Kittie M. vein. See Matoa vein. 

Klondike vein, location and description of. 156, 

391,392,393,404 

Knight, F. C., analyses by. 118,202 

Knowlton, F. H., fossil determined by. 31 

Krennerite, description of. 116 


Page. 

Krennerite, occurrence of. 4,114,175 

Kurie, F. M., data from. 431 

Kurtz vein, location and description of. 475-476 


L. 


La Bella shaft, location of. v . 426 

La Bella vein, location and description of. 160, 

417-418.422.424.427,428.429 

structure of, figure showing. 160 

Labor, conditions of. 5,142-143 

Labradorite, description of. 127 

occurrence of. 103,114 

Lantishie claim, location of... 314 

Last Chance claim, location and description of. 287 

Last Dollar Gold Mining Company, mines of. 374 

Last Dollar mine, description of. 374-377 

gas in. 254,261 

geology of. 374 

location of. 6.149,374 

metasomatism in. 188,190 

minerals in... 116,120,121,122,124,125,126,188,200.375-377 

ore of. 170,174,375 

photomicrographs of. 180 

oxidation in. 198 

production of. 374 

rocks in. 32,85 

temperatures in. 270 

veins in, character of..... 157,163,173,177,374,375-377,382 

figure showing. 161,376 

water level in. 240,242,245 

change in, figure showing. 242 

workings of. 374,438 

Last Dollar vein, location and description of. 374-377 

Latite-phonolite, abundancy of.. Ill 

alteration of. v . 184,189-191 

analyses of.. 69,79,104,189 

area covered by. 110 

composition of. 57,69,79-83 

definition of. 68-70 

description of. 68-71 

eruptions of. 24 

fissures in. 159 

' intrusions of. 32-34 

minerals in. 81,83 

occurrence of. 2, 

3.21,32-34,70,98-99,291,309,311. passim 362-495 

origin of. 56 

petrology of. 71-77 

photomicrographs of.1. 82 

texture of. 78 

trachytic facies of. 77-78 

analysis of. 79 

transition of, to phonolite. 83-84 

Laura Lee mine, location and description of. 271 

minerals in. 115,271 

Lavenite, description of. 64-65 

occurrence of. 65 

Lead, occurrence of. 225 

Lead ores, occurrence of. 169,172,286 

value of. 170 

Lead vein, character of. 174,302,303 

Lead-zinc veins, occurrence and description of. 182 

Leasing, prevalence of. 5,134,143 

Le Clair claim, location of. 322 

ore of. 210-211 

Le Clair vein, location and description of_ 322,324,326-328 

Lee, H. A., on mine gas. 259 




























































































































INDEX. 


507 


Page. 

Lee shaft, location of. 389 

veins at, section of, figure showing. 390 

Lee veins, location and description of. 157, 

174,440, 441,443,444,448 

Legal Tender mine, ore bodies in. 212 

vein structure in, figure showing. 160 

Legal Tender vein, location and description of... 426-427,429 

Leucite, occurrence of. 67-68 

Leucitophyre, occurrence of. 67 

origin of. 56 

petrology of. 67-68 

Lexington mine, ore of. 296 

veins of. 294,306 

Lillian Leland claim, location of. 291 

Lillie Gold Mining Company, mine of. 424 

Lillio mine, description of. 424 

dipin. 156 

history of. 145 

location of. 5,149,408 

ore of. 424 

production of. 149,424 

veins of, character of. 206,424 

section of, figure showing. 423 

water level in. 240,244,245,246,424 

change in, figure showing. 242 

workings of. 151,244,408,424 

Lillie vein, character of. 206,277,278 

Lillie-Vindicator shoot, length of. 206 

Limonite, description of. 123 

occurrence of_ 4,55,114,183,199,200,202,283,285,286,391 

Lincoln mine, location of. 151 

Lincoln Mines Mining and Milling Companj T , mines of. 283 
Lincoln vein. See Virginia M. vein. 

Lindgren, Waldemar, work of. 14,42 

Lindsay vein, location and description of. 360 

Literature on the district. 15-17 

Little Annie Rooney claim, location of. 297 

Little Clara claim, location of. 314,347 

Little Grant claim, location of. 314 

Little Joe claim, location of. 387 

Little May mine, minerals in.'.1. 116 

ore of. 354 

Little Montana claim, location of. 487 

Little Pedro claim, location and description of. 288 

Little Pisgah Peak, rocks of. 58 

Lode fissures, area of. 153-155,167 

character of. 155 

convergence of. 155,167 

description of. 6,153-168 

dip of_-. 156 

direction of. 155-156 

plate showing. 154 

distribution of. 153-155 

filling of. 173-182 

influence of country rock on. 159-160 

intersections of. 156,165-167 

minerals in. 114-129,173-176 

origin of. 167-168 

persistency of. 156 

sheeted structure of. 155 

See also Sheeted zone. 

structure of. 160-165,176-182 

width of. 153 

See also particular mines; Veins; Ore deposits; 

Gold deposits; etc. 

Logan mine. See John A. Logan mine. 

Logan vein, character of. 381 


Page. 

Londonderry mine, location and description of. 367 

London vein, character of. 456,463 

Los Angeles mine, location and production of. 380,383 

| Lost Anna vein, location and description of. 120, 

121,174,442,443 

I Lovenite, occurrence of. 219 

Lovett vein, location and description of. 198,367-368 

| Lowell shaft, location and description of. 433 

Lower Trail tunnel, rocks in. 33 

Lucky Dick claim, location of. 478 

| Lucky Gus mine, ore of. 383 

production of. 380 

• rocks in. 30,98 

vein in. 382 

workings of. 382-383 

Lunge, -—, air-testing device of. 253 

Lyons shaft .location of. 399 

M. 

Mabel M. mine, location and description of. 358-361 

minerals in. 116 

veins of. 360-361 

water in. 361 

workings of. 358 

Maggie claim, location of. 466 

Maggie prospect, dike on. 368 

Magmas, crystallization from, products of. 101 

differentiation of. 3,113 

Magna Charta claim, location and description of. 286 

Magnesium, presence of, in vein-forming water. 222 

Magnetite, description of. 123 

occurrence of. 48, 

49,52,64,67,77,78,81,83,99,114,185,188,192,193,194 

Main vein, location and description of. 417,420-421 

Mallardite, description of. 126 

occurrence of. 114 

origin of. . 201 

Maloney vein, location and description of . .. 292,294,296-297 

section of, figure showing. 296 

Maloney shaft, location of. 396 

Mammoth claim, location of. 478 

Manganese, occurrence of. 203,285,366,374 

Manganese vein, location and description of. 211,373-374 

Map of district. Pocket 

revision of. 1,11-12 

Map, geological, of district. Pocket 

of Portland mine. 434 

Man, index, showing location of district. 12 

Marcasite, description of. 120 

occurrence of. 114 

Maroon Tunnel Company, mine of. 404 

Mary Ann mine, description of. 347 

ore bodies in. 211,305,347 

Mary Ann Mining Company, mine of. 347 

Mary Cashen mine, vein of. 489 

Maryland claim, location of. 298 

Mary McKinney Company, mine of. 322 

Mary McKinley mine, description of. 321-330 

dip in. 156 

drainage of. 237,321 

gas in. 261 

geology of. 322,323 

history of. 322 

location of. 5,148 

minerals in. 120,128,174,185 

ore deposits in. 206,210,213,327,329 


























































































































508 


INDEX. 


Page. 

Mary McKinley mine, production of. 148 

rocks in. 26,91 i 

sorting at. 137 

section of, figure showing. 325 

temperatures in. 269 j 

veins of, character of. ; . 162, 

163,164,165,166,173,176,178,179,324-328 

plan of. 323 

water level in. 234,240,329-330 

change in. 237,248,329 

figure showing. 242 

workings of. 322 

Mary McKinney veins, location and description of.... 322, 

324,326-328 

Mathews, E. B., on granite. 43,101-102 

Matoa Gold Mining Company, mines of. 292 

Matoa vein, location and description of. 162-166 

292,294-295,297,309,311,312 

Mattie D. claim, location of. 314 

workings on. 315 

Mattie D. vein, location and description of. 164, 

315,317,318,321 

Mattie L. claim, location of. 292 

Mayflower claim, location of. 283,322 

May mine, minerals in. 126 

May Queen claim, location of. 292 

Melonite, description of. 116 

Mercer, D. N., mine of. 402 

Mercer mine, description of. 402-403 

Mercer vein, minerals in. 115 

Metallic tunnel, location and description of. 280 

Metamorphic rocks, classes of. 101 

description and petrology of.3,48-53 

Metasomatism, agencies of. 184,196 

minerals produced by.85-88 

sequence of...».. 195-196 

vein formation and, relations of. 7,184-204 

See also particular mines; Alteration; Oxidation; 

Hydrometamorphism; Water. 

Mica, occurrence of. 73,77,184,185,188,192 

Microcline, description of. 127 

occurrence of. 46, 

47,49,50,72,100,114,193,194,436,442, 447 

Microperthite, occurrence of. 44,46,47,72,193 

Middle vein, location of. 427 . 

Midget Gold Mining Company, mine of,.. 298 

Midget mine, description of. 297-305 

dikes in. 91 

fissures in. 153 

geology of. 300-301 

location of. 5,148,298 

minerals in. 121,192 j 

ore of.:. 158,206.302-305 

production of. 148,298 ! 

relations of Conundrum mine and, figure showing . 300 

rocks in. 25 

veins in, character of. 165,174,177,200,302,304-305 

ventilation of, figure showing. 263 

view of.'. 18 

water level in. 241 

change in, figure showing. 242 

workings in. 298 

plan showing. 299 

Midget vein, location and description of. 298,302-304 

Midland claim, location of. 291 

Milling, stamp, inefficiency of. 138 

Mineral Hill, placers near. 5,152 

ptospects on. 151,271 


Page. 

Mineral Hill, rocks on. 22,97,271 

Mineral Rock shaft, rocks in. 382 

Mineral Rock vein, location and description of. 380, 

382-383, 411 

Minerals, amount of, in solutions. 153 

descriptions of. 114-129,173-175,185-188 

derivation from. 9 

list of. 4 

occurrence of. 114-129,173-176,185-188 

paragenesis of. 175-176 

See also particular mines, tunnels, etc. 

Mines, descriptions of. 271-496 

distribution of. 147-151 

drainage of. 9-10 

gas in. See Gases, mine. 

list of. 5 

production of. 4 

restricted area of. 5 

returns from. 5 

underground workings of. 5 

plans showing.26, Pocket 

ventilation of. 253 

figure showing. 263 

water level in, position of, diagrams showing.... 236,242 

Mining, cost of. 4,137,145 

development of, history of. 130-146 

methods of. 4,135-137 

review of. 5,147-152 

Mining companies, flotation of. 143-144 

Mint mine, description of. 306-308 

gas in. 262 

ore in. 307-308 

rocks in. 26,306 

veins of. 307-308 

workings of. 306 

Mirabilite, description of. 126 

occurrence of. 114 

Mitre Peak, rocks of. 58 

Modoc mine, description of. 378-379 

dikes in. 378,381 

gas in. 261,378 

geology of. 378 

location of. 149,378 

minerals in. 125 

ore of.212,379 

oxidation in. 198 

production of. 378 

veins of. 378-379,382 

water level in. 242,378 

workings of. 378 

Modoc Mining and Milling Company, mine of. 378 

Modoc vein, location and description of. 375,377 

Moflatt vein, character of. 371 

Mohawk Belle mine, description of. 347 

Moissan Henri, analysis by. 257 

Molly Kathleen mine, description of. 274-275 

dikes in. 32,95,274-275 

gas in. 262 

location of. 274 

production of. 151,274 

rocks in. 85 

veins in. 156,157,158,274-275 

workings of. 274 

Molybdenite, deposition of. 225 

description of. 120 

occurrence of. 4,6,114,169,174,176, 

190,191,195,340,375,376,411,414,418,464,473,474 
oxidation of. 200 






























































































































INDEX. 


Page. 

Molybdenum, occurrence of. 172,225,484 

value of. 170 

Molybdite, description of. 123-124 

occurrence of. 4,114 

Monarch claim, location of. 478 

Monehiquite, abundance of. Ill 

analyses of. 9G, 104 

area covered by. 110 

composition of. 96 

description of. 95 

occurrence of.:. 3,273,368,417,339 

origin of. 56 

petrology of. 95-96 

photomicrograph of. 94 

Montana dike, location and description of. 480, 

485-486,489-490 




Montana vein, location and description of. 159, 


166,488-489,493 

Montreal Gold Mining and Milling Company, mines of.. 280 

Monument Gold Mining Company, mine of. 475 


Monument mine, description of. 475-476 

dike in. 476 

geology of. 476 

ore from. 476 

analysis of. 117 

veins in. 158,475-476 

workings of. 471,475 

Monument vein, character of. 475-476 

Moon-Anchor Consolidated Gold Mines, mine of. 297 

Moon-Anchor mine, description of. 297-305 

geology of. 300-301 

history of. 145,297-298 

location of. 5,148,297 

minerals in. 116,121,124,126,174 

ores of. 302-305 

oxidation in. 198 

production of. 148,298 

veins in, character of. 159,163,164,174,302,304-305 

water level in. 234,241,297,298,305 

change in, figure showing. 242 

workings in. 298 

plan of.•.. 299 

Moore, C. J., reports of. 233 

Moose dike, character of. 342,343 

Moose Gold Mining Company, mine cf. 341,369 

Moose mine, description of. 341-345 

dike in. 93,342 

fissures in. 153 

gas in. 254,258,260-261,345 

geology of. 342-343 

history of. 341-342 

location of. 5,148 

minerals in. 120,121,122 

ore of. 201,203,213,343-345 

analyses of. 172,202 

production of. 148,342 

section of, figure showing. 344 

silver in. 203 

veins of. 343,344 

water in. 345 

workings of. 342 

plan of. 343 

Morencite, description of. 129 

occurrence of. 114,129,200 

Morning Glory Gold Mining Company, mines of. 314 

Morning Glory group, location of. 314 

view of. 292 


509 


Page. 

Morning Glory mine, coal in.31,317 

coal in, analyses of. 31 

description of. 314-321 

geology of. 317 

history of. 314-315 

location of. 5,314 

ore from. 318-321 

photomicrograph of. 180 

veins of.317-318,319-321 

water level in. 240,321 

change in. 321 

figure showing. 242 

workings of. 315,317 

plan showing. 316 

Morning Glory Mining and Leasing Company, mines of. 314 

Morning Glory vein, location and description of. 320,321 

Morning Star mine, location and history of. 383 

Mountain Beauty claim, location of. 409,411 

Mountain Boy Gold Mining Company, mine of. 365 

Mountain Girl claim, location of. 347 

Mountain Monarch mine, minerals in. 122 

Mount Pisgah mining district, organization of. 130 

Mudd, W. S., on mine drainage. .. 10,233,247-249 

Murphy mine, description of. 403 

Murphy shaft, character of. 394,395 

Murray veins, location and character of. 302,304 

Muscovite, description of. 128 

occurrence of. 46,47,48,49,51,52,114,192 

Muscovite schist, analysis of. 53 

See also Schist. 

N. 


Nagyagite, description of. 116 

Natrolite, description of. 127 

occurrence of. 114 

Necessity claim, location of. 478 

Nepheline, description of. 127 


occurrence of. 58,61,67,86,103,114 


Newell tunnel, location of... 235,496 

New Haven Gold Mining Company, mine of. 345 

New Haven mine, description of. 345-346 


ore bodies in 


211,346 


production of. 345 

veins in. 158,346 

New Moon claim, location of. 297 


New vein, location and description of- 307,308,417-418,422 

New York tunnel, location and description of. 365 

New Zealand Mining Company, mine of. 404,406 

Nipple Mountain, rocks of. 58 

Nitrogen, excess of, danger from. 253 

occurrence of. 259-260 

Nolan tunnel, location and description of. 27.5-276 

Normandy shaft, location and description of. 283 

North Star dike, character of. 317 

North Star mine, dikes in. / ... 36 

workings of. 317 

North Star veins, location and description of.318,321 

Nosean, description of. 127 

occurrence of. 61,67,74,81,83,86,103,114 


0 . 


Ocean Wave claim, minerals on. 128,183 

Old Gold mine, geology of. 356 

location of. 148,355 

ore of.*. 356-357 

production of. 355 

veins of. 356-357 


13001—No. 54—06-34 





































































































































510 


INDEX 


Page 

Old Gold mine, view of. 350 

workings of. 356 

Old Gold Mining Company, mines of. 355 

Old Hickory claim, location of. 349 

Oligoclase, description of. 127 

occurrence of. 44,83,114.193,194 

Oliver shaft, location of. 4S4 

Olivine, description of. 127 

occurrence of. 53-54,55,64,92,93,95,103,114 

Olivine syenite, composition of. 102 

description of. 53 

occurrence of. 53 

petrology of. 53-55,102 

See also Syenite. 

Opal, description of. 123 

occurrence of. 4,100,114,169,174,176,178,402 

Ophelia tunnel, description of. 291 

dike in. 93,324 

drainage by. 9,235,242,244 

gas in. 254,256,269 

location of. 291,322 

minerals in. 124,125,126,128,174,175,177,183 

ore from, photomicrograph of. 180 

rocks in. 26,85 

temperatures in. 270 

yeins in, character of. 163,174,182 

Ophir Mining and Milling Company, mine of. 484,495 

Ore bodies, description of, terms used in, diagram 

showing. 206 

occurrence of, method of, plan showing. 212 

See also Ore deposits; Lode fissures; Ore shoots; 

Veins; Ores; Gold deposits; etc. 

Ore deposits, conclusions on. 8-9 

depth of. 32 

distribution of. 5,140,146,147 

enrichment of. 203-204 

genesis of. 8-9,217-231 

inconspicuousness of. 134,154 

metasomatism of. 184-185,188-196 

mining and milling of. 4-5,135-142 

technology of. 5,140-142 

oxidation of. 196-204 

production of. 4,134-135 

See also Ores; Ore bodies; Ore shoots; Veins; Gold 
deposits; etc. 

Orehouse tunnel, location of. 315 

Ores, analyses of. 172,173 

character of. 6,7,169-170 

chlorination of. 139 

composition of. 170-173 

cyanidation of. 139 

depth and relations of. 8 

description of. 137,169-183 

milling of. 138-139 

mineralogy of. 173-176 

occurrence of. 6-7 

origin of.217-231 

oxidation of. 169-170 

photomicrographs of. 180,186 

sorting of. 136-137 

smelting of. 4,139 

structure of. 176-182 

tenor of.... 6-7,8.170-173,223 

treatment of, cost of. 145-146 

value of.*. 170-173 

varieties of. 182-183 

See also particular mines; Ore deposits; Gold 
deposits; etc. 


Page 

Ore shoots, country rock and, relations of. 208-209 

depth and, relations of. 207-208,214-216 

description of. 205-216 

synopsis of. 8 

terms used in, diagram showing. 206 

intersections of veins and, relations of. 209-213 

pitch of. 206 

shape of. 205-208 

plate showing. 206 

surface and, relations of. 207-208 

veins and, intersections of. 209-213 

vertical range of, plate showing. 206 

Ore vein, character of. 287 

Orizaba claims, location of. 349 

Orpha May mine, dikes in. 381 

gas in. 261,380 

location of. 5,149 

minerals in. 124,176 

ore bodies in. 212 

production of. 380 

vein of. 380,382 

water level in.:. 240,244 

change in, figure showing. 242 

workings in. 380,383 

Orpha May vein, location and description of. 380.382 

Orpha Nell claim, location of. 478 

Orphan shaft, character of. 396 

Orthoclase, description of. 127 

occurrence of. 44 

46,47,49,51-52,53,56,67,68,72,73,81.83,85 
86,92,95,100,103,114,174,183,188,194,443 

Osmotic hypothesis, G. F. Becker on. 229 

Oxidation, alteration due to. 7,184,196-204 

depth of.7,196 

effects of. 203-204 

processes of. 199-203 

structure resulting from. 199 

water level and, relations of. 198-199 

See also particular mines, localities, etc.; Metaso¬ 
matism; Hydrometamorphism; Water; 
Alteration. 

Oxides, etc., description of. 122-129 


P. 


Palache, Charles, on sylvanite. 116,360 

Paragenesis of minerals, discussion of. 175-177 

Parallel vein, location and description of. 371,489 

Parker & Head vein, location of. 360 

Par Value vein, character of. 476 

location of. 314 

Pay Rock claim, location and description of. 279 

Pearce, Richard, on oxidation. 201,203,204 

on sylvanite. 116 

Pearl mine, location of. 406,478 

Peggy mine, description of. 330 

Peggy vein, character of.211,330 

Pegmatite, description and petrology of. 48 

Penrose, R. A. F., on Anna Lee chimney. . 447-448 

on discovery of gold. 130 

on granite ore. 193 

on kaolin. 128 

on metasomatism. 195-196 

on Orpha May vein. 382 

on placers. 152 

onpyrite. 170 

on Raven dike. 336,338 

work of.1,4,11,147,171 































































































































INDEX 


511 


Page. 

Petrology of district. 101-113 

Petrology of metamorphic and igneous rocks.3,41-113 

Petzite, description of. 116 

occurrence of. 114 

Pharmacist Consolidated Mining Company, mine of... 399 

Pharmacist mine, description of. 399-401 

dipin. 156 

location of. 5,399 

minerals in. 123 

ore of. 400-401 

production of. 399 

rocks in. 34,400 

veins of. 149,393-395,400 

workings of. 399-400 

Pharmacist vein, character of. 159 

166,391,393,395,397,400,401 

ore shoots on. 212 

stereogram showing. 211 

Phonolite, abundancy of. Ill 

alteration of.... 184,188 

analyses of. 66,104 

area covered by. 110 

composition of. 66-67 

definition of. 57 

description of. 1,57-58 

dike of, intersection of sheeted zone and, ore at, 

figure showing. 212 

dikes of. See Dikes, phonolite. 

fissures in.,. 164 

intrusions of. 24,38,58 

minerals in. 67 

occurrence of. 1-3,19,20,34-37, ^7-58,98-99, passim 271-496 

origin of. 56 

petrology of. 59-67 

photomicrographs of. 60 

texture of. 58,65-66 

transition of, to latite-phonolite. 83-84 

Phonolitic breccia, occurrence of.20 

Photomicrographs of rocks. 60,82,94 

Pikes Peak, rush to. 130 

views of. 18,34,280,362 

Pikes Peak granite, analyses of. 45 

description of. 3,43,45-46,47,193 

fissures in. 159 

occurrence of. 20,23,29,34, 

279,281,314,334,337,349-352,356-358,430,467,495 

petrology of. 43-45 

Pikes Peak mine, production of. 380 

workings of. 382 

Pikes Peak vein, location of. 149,411 

Pilgrim tunnel, rocks in. 88 

Pinnacle mine, description of. 383-384 

location of. 149,383 

veins ir^, character of. 206,383-384 

workings of. 383 

Pinto dike, location and description of. 93, 

166,212,393,394,396-397,399 

ore shoots on. 36 

stereogram of. 211 

Pinto mine, description of. 396 398 

dikes in. 36,97,396 

geology of. 396-397 

location of. 396 

ore of...-. 212 

veins of. 397-398,411 

stereogram showing. 211 

workings of.-. 396 

Pinus, occurrence of. 31 


Page. 

Pisgah, Mount, rocks of. 34,97 

view of. 18 

See alio Mount Pisgah mining district. 

Placers, occurrence of. 5,152 

Plagioclase, occurrence of. 43-44,46,47,49,72,73,86,93 

Plymouth Rock mine, description of. 285 

location of. 148,285 

minerals in. 174 

oxidation in. 197 

workings of. 285 

Pointer mine, description of._. 306-308 

dike in. 95 

gas in. 262 

minerals in. 121,122,124 

ore of. 171,174,307-308 

rocks in.1. 32,306-307 

veins in, character of. 162,179,307-308 

workings of. 306 

Pointer vein, location and description of. 307 

Porcupine shaft, location of. 382 

Porphyries, character of. 2 

occurrence of. 2,20 

Porter Gold King mine. See E. Porter Gold King 
mine. 

Portland mine, description of. 430-449 

dikes in. 438-439 

structure of, plate showing. .<. 166 

chlorination mill at, process in. 142 

development of. 133 

dikes in. 91,93,95,381 

drainage of. 242,449 

geology of. 433-439,457 

map showing. 434 

history of. 131,144-145,430-431 

locating of. 4,430 

location of. 5,150,430 

minerals in. 116,118,120,121,122,126,128,129 

mining in. 135-136 

ore of. 171,172,174,208,212,214,442-448 

value of. 448 

plan of. 432 

production of. 135,150,431 

rocks in. 27-29,32,33,85,98,209 

analyses of. 79,87 

sections of, figures showing. 140,433 

sorting at. 137 

valuation of. 144 

veins in, character of. 154,157,159,160,162, 

163,164,173,174,177,179,205,439-442,443-448,452 

figure showing. 162,164,166 

view of. 430 

water level in. 197,234,240,449 

change in. 242 

figure showing. 242 

workings of. 431-433 

maps showing. 432,434 

Portland vein, location and description of. 435, 

438,439,440,446 

Potassium, presence of, in vein-forming water. 222-223 

Potter vein, character of. 292,294 

Poverty Gulch, dikes in. 32,271-272 

drainage of. 244 

exploration in. 130,131 

gold in. 4 

mines in. 5,147,271-279 

oxidation in.*. 198 

rocks in. 25,32,70,271 

Precipitation, amount of. 233 































































































































512 


INDEX. 


Page. J 

Prince Albert mine, description of. 358-361 

geology of. 359 

location of. 5,148,358 

minerals in. 360 

ore body in. 209 

sections of, figure showing. 208 

ore of.-. 360-361 

analysis of. H7 

rocks in. 35 

veins of. 165,360-361 

w r ater in. 361 

workings on. 358 

Prince Albert Mining Company, mine of. 358 

Princess Alice Gold Mining Company, mine of. 379 

Princess E. claim, location of. 331 

Prior, G. T., and Smith, G. F. H., on calaverite. 116 

Production, future of. 9,231-232 

value of. 4,133,134-135 

See also particular mines. 

Progress workings, rocks in. 293 

Proper vein, character of. 272,273 

Prospect mine, minerals in. 122 

Protection claim, location of. 298 

Providence shaft; location of. 488 

Psilomelane, description of. 123 

occurrence of. 4,114,287 

Pueblo mine, description of... 403 

Pumping, beginning of. 133,234 

effect of. 239-242 

records of...... 9-10 

Puzzle vein, minerals in. 120,121,122,127,174,178 

Pyrite, description of. 120 

occurrence of. 4, 47, 77, 86, 98, 100, passim 174-493 

oxidation of. 200 

Pyroxene, description of. 128 

occurrence of. 53,73,85,86,89,95,185,322,384 

Q. 

Quartz, description of. 123,181 

fluid inclusions in. 181 

occurrence of. 4, 6, 44-54, 77, passim 114-493 

R. 

Raaler claim, vein of. 356 

workings on. 355 


Railroads, construction of... 4,132,133 i 


Ramona No. 2 mine, description of. 363-364 

dike in. 363-364 

ore of. 364 

workings of. 363 

Ramona vein, location and description of.211,363 

Ransome, F. L., work of. 14,42 

Raven dike, location and character of. .. 332,335-336,337-338 

Raven Hill, drainage of. 235,244 

mines on. 148,314-349 

view of. 292,332 

rocks of. 35,147 

south slope of, mines on. 5,314 

mines on, view of. 332 

view from. 350 

Raven mine, location of. 531 

minerals in. 126 

ore from, analysis of. 117 ! 

Raven tunnel, dike in. 96 

Raven vein, location and description of... 332-333,338 

Rebecca Gold Mining Company, mine of. 272 

Red Mountain, mines on. 280-281 

rocks of. 47,281 


\ 

Page. 

Red Rock shaft, rocks in. 30 

Red Spruce mine, description of. 306-308 

ore from. 171,307-308 

rocks in. 306-307 

veins of. 307-308 

workings in. 306 

Reduction, costs of. 145-146 

processes of. 4-5,138-140 

Reed Investment Company, property of. 370 

Replacement deposits, occurrence of.6,153,195 

Republic claim, location of. 322 

workings on. 322 

Requa, B. F., development by. 130 

Revenue mine, ore bodies in. 212 

Revenue vein, location and description of ... 426,427-428,429 

Rhodochrosite, description of. 124 

occurrence of. 4,114,169,174,178,303,307,108 

Rhyolite, age of. ICO 

association of grits and. 2,100-101 

description of. 100-101 

occurrence of. 19,100 

origin of.56-57 

petrology of. 100 

Rhyolite-Beacon Gold Mining Company, shafts of... 279-280 

Rhyolite Mountain, geology of. 279 

minerals on. 123 

mines on. 280 

prospects on. 151,279-280 

rocks of. 20,34,57,97,279 

view of. 18,280 

Rickard, T. A., on chlorination. 140 

on discovery of gold. 130-132 

on gypsum.. >. 284-285 

on Independence mine. 450 

on sylvanite. 116 

Rigi dike, location and description of.: 381 

Roanoke shaft, location and description of. 271 

Rock,'A. M., work of. 14 

Rocks, composition of, diagram showing. 112 

description and petrology of. 41-113 

divisions of. 3,42-43 

investigation of. 41-42 

oxidation of. 197 

photomicrographs of. 60,82,94 

See also Metamorphic rocks; Igneous rocks. 

Roscoelite, description of. 128 

occurrence of. 4, 

114,115,128,169,174,184,185,194,328,329,339 

Rose vein, location and description of. 439,440-441 

Royalties, amount of. 5 

Rubie mine, location and description of. 379 

ore bodies in. 211 

vein in. 382 

Rutile, description of.?. 123 

occurrence of. 55,114,184,188,190 


S. 


Sacramento mine, production of. 380 

Safety shaft, rocks in. 29,495 

St. Patrick mine, view of. 34 

water level in. 240 

change in, figure showing. 242 

Sampling, cost of.•. 138 

employment of. 4,138 

plants for, list of. 138 

process of. 138 

Sanidine, occurrence of. 100 



































































































































INDEX 


513 


Page 

Saunders shaft, character of. 394,395 

Sehaller, W. T., analysis by. 52-53,92-93,126,189,192 

on emmonsite. 119 

Schist, alteration of. 184,192 

analysis of. 53 

description of. 3,19,51 

occurrence of. 1, 

19-20.23,271,276-277,281.288,311-312,356,367-368 1 

petrology of. 51-53 j 

Scranton mine, workings of. 433 

Scranton vein, location and description of. 439,440-441 

Sections, geological, figures showing. 37,148; Pocket 

Sedan shaft, location and description of. 281 

Sedimentary deposits, occurrence and character of. 22-23,37 

Sericite, occurrence of. 4,50,55,59,86,1S4-195.340,484 • 

Serpentine, description of. 128 

occurrence of. 54,73,96,114,128,187,188,190,192,195 

Shaft vein, location and description of. 435 

Sheeted zone, description of. 160-165 

figure showing. 162 

fissures of. 16 -165 

intersection of phonolite dike and, OTe at..•_ 164 

figure showing. 212 

occurrence of. 6,159,160-165 

oxidation of... 199 

Sheriff mine, description of. 364-365 

ore in.;... 211,364-365 

veins in. 158,364 

workings of.!. 364 

Sheriff Gold Mining Company, mine of. 364 

Shurtloff mine, description of. 409-412 

geology of. 409 

location of. 408,409 

ores of. 411-412 

production of. 409, 

veins of. 212,410-411 

workings of. 409 

Shurtloff No. 1 vein, location and description of. 380-381,383 

Shurtloff vein, location and description of.212,411-412 

Siderite, occurrence of. 187,188,190 

Sigel vein, location and description of. 416,417-418,422,427,428 

Silica, deposition of. 229 

presence of, in vein-forming water. 217 

Silicates, description of. 122-129 

Silicification, occurrence of. 195 

Sillimanite, occurrence of. 49,50,52,192 

Silver, description of. 115 

occurrence of. 7,169,171, 

182,275,289,303,307,311,319,343,356,379,402,414,418 

production of. 431 

Silver ores, oxidation of.. 203-204 

Sioux Falls and Cripple Creek Gold Mining Company, 

mines of. 280 

Smelting, adoption of. 139 

Smith, A. Mica, on mine gas. 259 

Smith, G. F. H., and Prior, G. T., on calaverite. 116 

Smith-Reilly vein, character of. 318,321 

Snide claim, description of. 331 

Sodalite, description of. 127 I 

occurrence of. 61-62,74,81,83,86,103,114,219 

Solutions, vein-forming. See Water, hot ascending. 

Sorting, methods of. 136-137 j 

South Park shaft, location and description ol. 286 i 

South shaft, location of. 471 ! 

Specimen mine, production of. 380 

Specularite, description of. 123 

occurrence of. 114,169,185 

Sphalerite, deposition of. 225 


Page- 

Sphalerite, occurrence of. 4,6,169,174,175,176,178, 

193,194,275,303-304,307,311,353,443,473.475,493 

Sphene, occurrence of. 78 

Spring Creek granite, description of. 3,47 

occurrence of. 20,23 

petrology of. 47 

Springs, occurrence of. 244 

Spur vein, location and description of. 164,489,490,492 

Squaw gulch, mines on. 287-288 

placers in. 152 

Squaw Mountain, views from. 34,362 

Standard drainage tunnel, drainage by_ 9,235,242,244,246 

Standard tunnel, location of. 315 

Steiger, George, analyses by. 79,182.183,239 

Stibnite, deposition of. 225 

description of. 120-121 

occurrence of. 4,6,114,169,174,353,350,372 

Stilbite, description of. 127 

occurrence of. 114 

Stonehouse vein, location of. 476,477 

Stoping, methods of. 135-136 

Stratton, W. S., development by. 4,131-132,430,449-451 

estate of, mines of. 276,284,285,292,380-383,401,408 

Stratton Cripple Creek Mining and Development Com¬ 
pany. See Stratton, W. S., estate of. 

Stratton’s Independence (Ld.), mine of. 449 

Stratton’s Independence mine, description of. 449-465 

development of. 136 

dip in. 153 

dikes in. 35,438,458-461 

drainage of. 238 

geology of. 457-461 

history of. 4,132,145,449-451 

location of. 5,449 

metasomatism in. 189-190,193 

minerals in. 116,120,121,128,172,189 

ore of. 171,193,203-204,213,450,461-464 

analyses of. 173,202 

oxidation in. 197 

production of. 135,150,451 

rocks in. 30,33,99,189 

analysis of. 189 

sections through, figures showing. 458,459 

section through Abe Lincoln mine and. 148 

tree stump in. 31 

valuation of. 144 

veins in. 132,150,156, 

157,158,159,162,165.167,206,215,452-456,461-464 

view of. 416 

water level in. 197,234,240,242,465 

change in. 238 

figure showing. 242 

workings of. 151,451 

maps showing. 454,455 

Stratton’s Independence-Portland shoot, length of ... 206 

Straub Mountain, prospects on. lgp. 495 

rocks of. 19,22,34,37,38,56,57,495 

section through Grouse Hill and, figure showing .. 37 

Strikes, occurrence of. 4,5,132-134,142-143,451 

Stringer lodes, occurrence of. 160 

Strong Gold Mining Company, mine of. 466 

Strong mine, description of. 466-471 

dikes in. 36,95,460,467-468 

geology of. 467-468 

location of. 5,150,466 

ores of. 469-470 

production of. 135,466 

veins of. 466,469-470 


/ 






























































































































514 


INDEX. 


Page. 

Strong mine, view of.:. 416 

water level in. 240,470-471 

change in, figure showing. 242 

workings of. 466 

Strontia, occurrence of, in vein-forming waters. 220 

Strontium sulphate, analysis of. 126 

description and occurrence of. 125-126,220 

Structure, account of. 2,23-40 

Sulphantimonites, description of. 120-122 

Sulphates, etc., description of. 122-129 

occurrence and source of. 220-221 

Sulphide enrichment, description of. 204 

Sulphides, deposition of. 229 

description of. 120-122,225 

presence of, in vein-forming water. 225 

Summit mine, minerals in. 123 

Sunflower shaft, location and description of. 271 

Sunnyside claim, location of.. 298 

Sunset claim, location of. 330 

Sunset-Eclipse mine, description of. 494-495 

geology of. 494 

minerals in. 122 

ore bodies in... 213 

production of. 494 

veins of. 494 

Sunshine mine, description of. 281-282 

production of. 281 

veins of... 282 

workings of. 281 

Swanson, Walter, data from. 279 

Syenite, abundancy of. Ill 

alteration of. 184,188 

analyses of. 87,104 

area covered by. 110 

composition of. 57,87-88 

description of. 84-85 

intrusions of. 32-34 

minerals in. 85-86 

occurrence of. 2,3,20,21,23,32-34,274, 

291,306-307.374,378,408,416-417,426,430,436-437 

origin of. 56 

petrology of. 85-87 

photomicrograph of. 82 

See also Olivine syenite. 

Sylvanite, composition of. 169 

description of. 116,169 

occurrence of. 4,114,131,169,178,303,307- 

308,311,318,337,341,343,344,360,372,442,475,476 
See also Tellurides. 

Synopsis of paper. 1-10 

T. 

Talbot vein, location of. 423 

Talc, occurrence of. 192 

Tateman shaft, location and description of. 426 

Tayfbr, E. G., vein found by. 355 

Teals tunnel, location of. 495 

Telluride mill, process in, description of. 142 

Tellurides, deposition of. 223-225,229 

description of. 115-118 

derivation of. 224 

occurrence of. 115-118, 

185-193,274,289,312,320-321,337-338,345, 348, 
356, 372, 373, 379,397-402,410 442, 475, 487 

oxidation of. 7,200 

See also Calaverite; Sylvanite. 

Tellurite, description of. 120 


Page. 

Tellurite, occurrence of. 114,120,289 

Tellurium, analysis of. 118 

occurrence of. 6,114,115 

oxidized compounds of, analyses of. 118 

descriptions of. 118-120 

presence of, in vein-forming water. 223-225 

value of. 170 

Temperature, underground, data on. 10,269-270 

Tenderfoot Hill, copper on. 115 

dike on. 32 

prospects on. 151 

Tertiary volcanics. See Volcanic rocks. 

Tetradymite, description of. 116 

Tetrahedrite, deposition of. 225 

description of. 121-122 

occurrence of. 4, 

6,7,114,169,174,175,188,204,212,272,278,286,307-308, 
318-320,327-329,343,353,372-379,391, 402, 411, 414, 418 

Theresa mine, description of. 426 

minerals in. 121 

veins of. 427,428,429 

Theresa East vein, character of. 427,428,429 

Thompson fault, location and description of.... 166,333,334 

Thompson mine, location of. 331 

ore of. 338,341 

workings on. 331,333-334 

Thurlow claim, location of. 322 

Tillery vein, location and description of. 351-352,353 

minerals in. 175 

Tipton, B. F., data from. 256,264 

Titanite, description of. 127 

occurrence of. 49,64,76-77,81,83,86,114 

Titanium, occurrence of. 56 

Topographical map of district. Pocket 

Topography, description of. 147,233 

development of. 36-40 

prevolcanic condition of. 36-38 

figure showing. 37 

Tornado claim, location of. 331 

workings on. 331-332 

Tourmaline, description of. 127 

occurrence of. 114 

Trachydolerite, abundancy of. Ill 

analyses of. 90,104 

area covered by. 110 

description of. 88 -89 

eruptions of. 24 

occurrence of. 2,3,21,34,322,324,387 

origin of. 56 

petrology of. 89-90 

photomicrographs of. 82,94 

texture of. 90 

See also Isabella trachydolerite. 

Trachyte, origin of. 56 

Trachyte mine, description of. 406 

minerals in. 122 

Trachyte Mountain, prospects on... 151,283 

rocks of. 3«, 57 

Trail mine, description of. 370 

dikes in. 370 

ore of. 211,370 

Trilby mine, description of. 369-370 

dikes in. 368,369-370 

location of. 370 

ore of. 369 

production of. 369 

Triumph shaft, location of. 482 



























































































































INDEX. 


515 


Page. 

Trotter claim, location of. 415 

Troutman, Fred, development by. 131 

Tuff, occurrence of. 98 

Tunnels, drainage, construction of. 235,246-247,250-251 

discharge by. 235-238,239-251 

figures showing. 236,242 

effect of. 9-10,239-246 

figures showing. 236,242,250 

location of. 235 

possible locations for. 246-247,249-251 

U. 

Union Gold Mining Company, mines of. 380 

United States Reduction end Refining Company, 

plant of, process in.,. 140-142 

V. 

Valencianite, occurrence of. 443,464 

Van Hise, C., on deposition. 231 

on gneiss. 48 

on tellurides. 223-224 

Vaughn shaft. See Glorietta shaft. 

Vein formation, alteration due to. 184 

Veins, composition of. 229 

formation of. 216 

intersections of, ore deposits at. 209-213 

metasomatism and, relations of.7,184-185 

minerals in. 114-129,173-176 

oxidation of. 198-199 

pitch of. 206 

structure of. 160-165,176-182 

plates showing. 160,162,164,166 

See also particular mines: Lode fissures. 

Ventilation, provision for. 253 

provision for, sections showing. 263 

Venture Corporation, mine of. 450 

Victor, fissures near. 154 

mines in and near. 5,476,477,487 

rocks near. 24 

view of. 34 

Victor Consolidated claims, location of. 478 

Victor Gold Mining Company, mines of. 387 

Victor mine, description of. 387-388 

geology of... 387 

location of. 5 

map showing. 388 

minerals in. 123 

ore in. 213,388 

production of. 149,387 

veins of. 156,387-388 

water level in. 234,244,245 

workings of. 387 

Vindicator Consolidated Gold Mining Company, mine 

of. 415 

Vindicator mine, description of. 415-422 

dike in. 95 

geology of. 416-417 

location of. 5,149,408,415 

metasomatism in. 190-191 

minerals in. 120,121,122.126,129 

ore of. 208,212,213,418 

oxidation in. 198,416 

production of. 149,415 

rocks in. 32-33,34,85 

analysis of. 189 

section of, figure showing. 420 

temperatures in.. 270 


Page. 

Vindicator mine, veins in, character of.156, 

157,158,173,206,417-422 

view of. 362 

water level in. 198,240,245,246,416 

change in, figure showing. 242 

workings of. 408,415 

figure showing. 419 

Vindicator vein, location and description of. 159,266 

production of. 159 

Virginia M. vein, location and description of. 309,310-311,312 

Vogesite, abundancy of. Ill 

analyses of.95,104 

area covered by. 110 

composition of. 93,95 

description of. 93 

occurrence of... 3,93,393 

origin of. 56 

photomicrograph of. 94 

petrology of. 93 

Volcanic cone, erosion of. 39-40 

formation of. 25,38 

• outline of. 25,38,40 

sections showing. 39 

Volcanic eruptions, date of. 1,2,23 

effects of. 2,21,24-25,36,38 

location of. 1,20,24 

products cf. 1,3,21 

Volcanic neck, carbonized wood in. 32 

fissures in. 154 

form of. 21,24-30 

intrusions in. 32 

Volcanic rocks, alkali-alumina and soda ratios of. 106 

alteration of. 184-185 

alumina-silica ratios of. 107 

analyses of. 66,79,87,90,93,95,96,104, 111 

discussion of. 20 

areas covered by. lio 

average rock of, composition of. 109-112,113 

composition of.. 66-67,79-83,87-88,90,92-93,95,96,104-112 

diagrams showing. 112 

explanation of. 107-109 

description of. 56-58,67,68-71,84-85,88-89,90-91,97-98 

divisions of. 56-57 

minerals in. 103 

occurrence of. 57-58,70,100 

origin of. 1,3,21,35-36,38,43 

oxides in. 105 

petrology of. 59-65,67-68, 

71-78,83-84,85-87,89-90,91-96,98-101,102-113 

potash-soda ratio of. 105 

succession of, order of. 113 

texture of.65, 78 

See also Igneous rocks. 

Volcano, exhalations from. 10,257-258 

Vulcan claim, location of. 349 

W. 

Wacu Weta mine, description of. 404 

Wad, description of. 123 

origin of. 201 

Wages, status of. 5 

Walden, Charles, data from. 375 

Wallace claim, location of. 415 

Wallace vein, location and.description of_ 417, 418, 421-422 

Walter claim, location of. 331 

Walter vein, location and description of. 164 

166,175,317-318,321,332-333,336-338 
Wardell vein, character of. 294-295,297 

























































































































\ 


t 


INDEX. 


516 


Page. 

War Eagle and Ramona mine, location of. 302 

ore bodies in. 211,363 

production of. 362 

veins of.... 363 

workings of. 362 

War Eagle vein, character of. 156,362 

Washington mine, locating of. 4,132, 450 

ore in. 461 

Water, hot ascending, composition of. 217-225 

deposition by. 8-9,226-231 

depth of. 226 

mode of. 228-231 

time of. 226-227 

source of. 227-228 

tem pe ratu re o f.-. 226 

See also Metasomatism; Hydrometamorphism. 

Water, underground, character of. 239 

decrease of, with depth. 248-249 

drainage of. 235-238,239-251 

by El Paso tunnel. 237,243 

figure showing. 236 

features of. 9-10,233-251 

level of... 233-234 

changes in.. 239-246 

plate showing. 242 

occurrence of. 279 

source of...,. 238-239 

storage of. 238 

temperature of. 239,270 

See also particular mines; Alteration; Oxidation; 
Metasomatism; Hydrometamorphism; 
Tunnels; Water level; Drainage. 

Water level, depth of. 197,233-234 

effect of drainage on. 239-246 

oxidation and, relations of. 198-199 

positions of. 7,9-10,197,234,239 

diagrams showing. 236,242 

See also Oxidation; Tunnels; Drainage; Water, 
underground. 

Wavellite, description of. 126 

occurrence of.. 4,114,176 

West Bobtail vein, location and description of. 452, 456 

West Independence vein, location and description of .. 452, 

456, 458 

West veins, location and description of. 411,471, 475 

West Victor vein, location of. 388,392 

Whisper block, development of. 370-371 

ore in. 211 

veins in. 371 

figure showing. 371 

Whisper vein, location and description of. 371 

Wild Horse mine, description of. 366-367 

gas in..,... 254,261 

location of. 149,366 

minerals in. 125 

ore in. 367 

oxidation in. 197 

production of...• 149 

veins in. 160,163,206,366-367 

water level in. 240 

workings of. 366 

Wild Horse vein, location and description of_ 362,366-367 

Wilkinson shaft, location of. 423 


Page. 

Willis, F. A., on Hull City mine veins. 413 

Wilson claim, location of.. 403 

minerals on.. 122 

Wilson Creek, placers on.. 152 

Wilson vein, location and description of. 393,397, 402-403, 411 

Winkler, Cl., on exhaust air. 253 

Winze vein, character of.—... 413,414 

Wisconsin mine, workings of. 433 

Womack, Robert, gold found by. 4,130-131 

Womack gneiss, description and petrology of. 48-50 

Wonderland claim, location of. 461 

Wood, H. T., gold discovered by. 130 

Woods Investment Company, mines of. 288, 

358,366,370,386, 404 

Wood vein, character of. 417,421 

Workings, underground, plans showing.26, pocket 

See also particular mines. 

Work Mining & Milling Company, mines of. 314 

Work vein, location and description of. 163, 

173,179,210,309,311,312,326,328 

World’s Fair claim, location and description of. 285 

W. P. H. mine, description of... 288-289 

location of. 149,288-289 

minerals in. 118,120,121,191,192 

ore of. 171,200,289 

production of.i. 289 

veins of.’.... 160,166,200,210,289 

workings of. 289 

W. P. H. vein, character of. 288,289 

Wrockloff mine, description of. 399 

dikes in... 393,399 

ore of. 399 

veins of, stereogram showing. 211,393 

Y. 

Yellow Bird claim, minerals on. 122 

Z. 

Zenobia mine, description of. 401-402 

location of. 5,380, 401 

minerals in. 115,123 

ore of. 400,401-402 

oxidation in. 198,201 

production of. 380,401 

rocks in. 34 

veins of, character of. 149,166,198,212 

workings of. 401 

Zenobia vein, character of. 400, 401-402 

Zeolite, occurrence of. 192 

Zinc, occurrence of. 225 

Zinc blende, occurrence of. 7,121,169,172,174,176,184,185,191, 
195,212,273,210-282,289,375-377, 379, 414, 418, 422, 428 

oxidation of. 200 

value of. 170 

Zinc-lead veins, occurrence and description of. 182 

Zircon, description of. 123 

occurrence of. 49,64,77,114,194 

Zoe mine, location and description of. 358-361 

shaft of. 358 

section through, figure showing. 351 

Zoisite, occurrence of. 55 














































































































CLASSIFICATION OF THE PUBLICATIONS OF THE UNITED STATES GEOLOGICAL SURVEY. 

[Professional Paper No. 54.] 

The serial publications of the United States Geological Survey consist of (1) Annual Reports, 
(2) Monographs, (3) Professional Papers, (4) Bulletins, (5) Mineral Resources, (6) Water-Supply 
and Irrigation Papers, (7) Topographic Atlas of United States—folios and separate sheets thereof, 
(8) Geologic Atlas of the United States—folios thereof. The classes numbered 2, 7, and 8 are sold 
at cost of publication; the others are distributed free. A circular giving complete lists can be had 
on application. 

Most of the above publications can be obtained or consulted in the following ways: 

1. A limited number are delivered to the Director of the Survey, from whom they can be 
obtained, free of charge (except classes 2, 7, and 8), on application. 

2. A certain number are delivered to Senators and Representatives in Congress for distribution. 

3. Other copies are deposited with the Superintendent of Documents, Washington, D. C., from 
whom they can be had at practically cost. 

4. Copies of all Government publications are furnished to the principal public libraries in the 
large cities thruout the United States, where they can be consulted by those interested. 

The Professional Papers, Bulletins, and Water-Supply Papers treat of a variety of subjects, and 
the total number issued is large. They have therefore been classified into the following series: A, 
Economic geology; B, Descriptive geology; C, Systematic geology and paleontology; D, Petrography 
and mineralogy; E, Chemistry and physics; F, Geography; G, Miscellaneous; H, Forestry; I, Irriga¬ 
tion; J, Water storage; K, Pumping water; L, Quality of water; M, General hydrographic investiga¬ 
tions; N, Water power; O, Underground waters; P, Hydrographic progress reports. This paper 
is the seventy-sixth in Series A and the ninety-fifth in Series B, the complete lists of which follow 
(PP=Professional Paper; B=Bulletin, WS=Water-Supply Paper): 

SERIES A, ECONOMIC GEOLOGY. 

B 21. Lignites of Great Sioux Reservation: Report on region between Grand and Moreau rivers, Dakota, by Bailey Willis. 
1885. 16 pp., 5 pis. (Out of stock.) 

B 46. Nature and origin of deposits of phosphate of lime, by R. A. F. Penrose, jr., with introduction by N. S. Shaler. 1888. 
143 pp. (Out of stock.) 

B ,65. Stratigraphy of the bituminous coal field of Pennsylvania, Ohio, and West Virginia, by I. C. White. 1891. 212 pp. 
11 pis. (Out of stock.) 

B 111. Geology of Big Stone Gap coal field of Virginia and Kentucky, by M. R. Campbell. 1893. 10 pp., 6 pis. (Out of 
stock.) 

B132. The disseminated lead ores of southeastern Missouri, by Arthur Winslow. 1896. 31 pp. (Out of stock.) 

B 138. Artesian-well prospects in Atlantic Coastal Plain region, by N. II. Darton. 1896. 228 pp., 19 pis. 

B 139. Geology of Castle Mountain mining district, Montana, by W. H. Weed and L. V. Pirsson. 1896. 164 pp., 17 pis. 

B 143. Bibliography of clays and the ceramic arts, by J. C. Branner. 1896. 114 pp. 

B 164. Reconnaissance on the Rio Grande coal fields of Texas, by T. W. Vaughan, including a report on igneous rocks from 
the San Carlos coal field, by E. C. E. Lord. 1900. 100 pp., 11 pis. (Out of stock.) 

B 178. El Paso tin deposits, by W. H. Weed. 1901. 15 pp., 1 pi. 

B 1§0. Occurrence and distribution of corundum in United States, by J. H. Pratt. 1901. 98 pp., 14 pis. (Out of stock; see 
No. 269.) 

B 182. A report on the economic geology of the Silverton quadrangle, Colorado, by F. L. Ransome. 1901. 266 pp., 16 pis. 
(Out of stock.) 

B 184. Oil and gas fields of the western interior and northern Texas Coal Measures and of the Upper Cretaceous and 
Tertiary of the western Gulf coast, by G. I. Adams. 1901. 64 pp.,10 pis. (Out of stock.) 

B 193. The geological relations and distribution of platinum and associated metals, by J. F. Kemp. 1902. 95 pp., 6 pis. 

B 198. The Berea grit oil sand in the Cadiz quadrangle, Ohio, by W. T. Griswold. 1902. 43 pp., 1 pi. (Out of stock.) 


I 


II 


SERIES LIST. 


PP 1. Preliminary report on the Ketchikan mining district, Alaska, with an introductory sketch of the geology of south¬ 
eastern Alaska, by A. H. Brooks. 1902. 120 pp., 2 pis. 

B 200. Reconnaissance of the borax deposits of Death Valley and Mohave Desert, by M. R. Campbell. 1902. 23 pp., 1 pi. 
(Out of stock.) 

B 202. Tests for gold and silver in shales from western Kansas, by Waldemar Lindgren. 1902 21pp. (Out of stock.) 

PP 2. Reconnaissance of the northwestern portion of Seward Peninsula, Alaska, by A. J. Collier. 1902. 70 pp., 11 pis. 

PP 10. Reconnaissance from Fort Hamlin to Kotzebue Sound, Alaska, by way of Dali, Kanuti, Allen, and Kowak rivers, 
by W. C. Mendenhall. 1902. 68 pp., 10 pis. 

PP 11. Clays of the United States east of the Mississippi River, by Heinrich Ries. 1903. 298 pp., 9 pis. 

PP 12. Geology of the Globe copper district, Arizona, by F. L. Ransome. 1903. 16S pp., 27 pis. 

B 212. Oil fields of the Texas-Louisiana Gulf Coastal Plain, by C. W. Hayes and William Kennedy. 1903. 174 pp., 11 pis. 
(Out of stock.) 

B 213. Contributions to economic geology, 1902; S. F. Emmons and C. W. Hayes, geologists in charge. 1903. 449 pp. (Out 
of stock.) 

PP 15. The mineral resources of the Mount Wrangell district, Alaska, by W. C. Mendenhall and F. C. Schrader. 1903. 
71 pp., 10 pis. 

B 218. Coal resources of the Yukon, Alaska, by A. J. Collier. 1903. 71 pp., 6 pis. 

B 219. The ore deposits of Tonopah, Nevada (preliminary report), by J. E. Spurr. 1903. 31 pp., 1 pi. (Out of stock.) 

PP 20. A reconnaissance in northern Alaska in 1901, by F. C. Schrader. 1904. 139 pp., 16 pis. 

PP 21. Geology and ore deposits of the Bisbee quadrangle, Arizona, by F. L. Ransome. 1904. 168 pp., 29 pis. 

B 223. Gypsum deposits in the United States, by G. I. Adams and others. 1904. 129 pp., 21 pis. 

PP 24. Zinc and lead deposits of northern Arkansas, by G. I. Adams. 1904. 118 pp., 27 pis. 

PP25. Copper deposits of the Encampment district, Wyoming, by A. C. Spencer. 1904. 107 pp., 2 pis. 

B 225. Contributions to economic geology, 1903, by S. F. Emmons and C. W. Hayes, geologists in charge. 1904. 527 pp., 
1 pi. (Out of stock.) 

PP 26. Economic resources of the northern Black Hills, by J. D. Irving, with contributions by S. F. Emmons and T. A. 
Jaggar, jr. 1904. 222 pp., 20 pis. 

PP 27. A geological reconnaissance across the Bitterroot Range and Clearwater Mountains in Montana and Idaho, by 
Waldemar Lindgren. 1904. 123 pp., 15 pis. 

B 229. Tin deposits of the York region, Alaska, by A. J. Collier. 1904. 61 pp., 7 pis. 

B 236. The Porcupine placer district, Alaska, by C. W. Wright. 1904. 35 pp., 10 pis. 

B 238. Economic geology of the Iola quadrangle, Kansas, by G. I. Adams, Erasmus Haworth, and W. R. Crane. 1904. 
83 pp., 11 pis. 

B 243. Cement materials and industry of the United States, by E. C. Eckel. 1905. 395 pp., 15 pis. 

B 246. Zinc and lead deposits of northwestern Illinois, by H. Foster Bain. 1904. 56 pp.. 5 pis. 

B 247. The Fairhaven gold placers of Seward Peninsula, Alaska, by F. H. Moffit. 1905. 85 pp., 14 pis. 

B 249. Limestones of southeastern Pennsylvania, by F. G. Clapp. 1905. 52 pp., 7 pis. 

B 250. The petroleum fields of the Pacific coast of Alaska, with an account of the Bering River coal deposits, by G. C. 
Martin. 1905. 65 pp.,7 pis. 

B 251. The gold placers of the Fortymile, Birch Creek, and Fairbanks regions, Alaska, by L. M. Prindle. 1905. 89 pp., 16 pis. 
WS 117. The lignite of North Dakota and its relation to irrigation, by F. A. Wilder. 1905. 59 pp., 8 pis. 

PP 36. The lead, zinc, and fluorspar deposits of western Kentucky, by E. O. Ulrich and W. S. T. Smith. 1905. 218 pp., 15 pis." 

PP 38. Economic geology of the Bingham mining district, Utah, by J. M. Boutwell, with a chapter on areal geology, by 

Arthur Keith, and an introduction on general geology, by S. F. Emmons. 1905. 413 pp., 49 pis. 

PP 41. Geology of the central Copper River region, Alaska, by W. C. Mendenhall. 1905. 133 pp., 20 pis. 

B 254. Report of progress in the geological resurvey of the Cripple Creek district, Colorado, by Waldemar Lindgren and 
F. L. Ransome. 1904. 36 pp. 

B 255. The fluorspar deposits of southern Illinois, by H. Foster Bain. 1905. 75 pp., 6 pis. 

B 256. Mineral resources of the Elders Ridge quadrangle, Pennsylvania, by R. W. Stone. 1905. 86 pp., 12 pis. 

B 259. Report on progress of investigations of mineral resources of Alaska in 1904, by A. H. Brooks and others. 1905. 
196 pp., 3 pis. 

B 260. Contributions to economic geology, 1904; S. F. Emmons and C. W. Hayes, geologists in charge. 1905. 620 pp., 4 pis. 

B 261. Preliminary report on the operations of the coal-testing plant of the United States Geological Survey at the Louis¬ 

iana Purchase Exposition, St. Louis, Mo., 1904; E. W. Parker, J. A. Holmes, and M. R. Campbell, committee in 
charge. 1905. 172 pp. (Out of stock.) 

B 263. Methods and cost of gravel and placer mining in Alaska, by C. W. Purington. 1905. 273 pp., 42 pis. 

PP 42. Geology of the Tonopah mining district, Nevada, by J. E. Spurr. 1905. 295 pp., 24 pis. 

PP 43. The copper deposits of the Clifton-Morenci district, Arizona, by Waldemar Lindgren. 1905. 375 pp., 25 pis. 

B 264. Record of deep-well drilling for 1904, by M. L. Fuller, E. F. Lines, and A. C. Veatch. 1905. 106 pp. 

B 265. Geology of the Boulder district, Colorado, by N. M. Fenneman. 1905. 101 pp., 5 pis. 

B 267. The copper deposits of Missouri, by II. Foster Bain and E. O. Ulrich. 1905. 52 pp., 1 pi. 

B 269. Corundum and its occurrence and distribution in the United States (a revised and enlarged edition of Bulletin 
No. 180), by J. H. Pratt. 1906. 175 pp., 18 pis. 

PP 48. Report on the operations of the coal-testing plant of the United States Geological Survey at the Louisiana Pur¬ 
chase Exposition, St. Louis, Mo., 1904; E. W. Parker, J. A. Holmes, M. R. Campbell, committee in charge. 1906. 
(In three parts.) 1,492 pp., 13 pis. 

B 275. Slate denosits and slate industry of the United States, by T. N. Dale, with sections by E. C. Eckel, W. F. Hille- 
brand, and A. T. Coons. 1906. 154 pp., 25 pis. 


SERIES LIST. 


Ill 


PP 49. Geology and mineral resources of part of the Cumberland Gap coal field, Kentucky, by G. H. Ashley and L. C. 
Glenn, in cooperation with the State Geological Department of Kentucky, C. J. Norwood, curator. 1906. 239 pp., 
40 pis. 

B 277. Mineral resources of Kenai Peninsula, Alaska: Gold fields of the Turnagain Arm region, by F. H. Moffit; Coal fields 
of the Kachemak Bay region, by R. W. Stone. 1906. 80 pp., 18 pis. (Out of stock.) 

B 278. Geology and coal resources of the Cape Lisburne region, Alaska, by A. J. Collier. 1906. 54 pp., 9 pis. 

B 279. Mineral resources of the Kittanning and Rural Valley quadrangles, Pennsylvania, by Charles Butts. 1906. 198 pp. 
11 pis. \ 

B 280. The Rampart gold placer region, Alaska, by L. M. Prindle and F. L. Hess. 1906. 54 pp., 7 pis. 

B 282. Oil fields of the Texas-Louisiana Gulf Coastal Plain, by N. M. Fenneman. 1906. 146 pp., 11 pis. 

PP 51. Geology of the Bighorn Mountains, by N. H. Darton. 1906. 129 pp., 47 pis. 

B 283. Geology and mineral resources of Mississippi, by A. F. Crider. 1906. 99 pp., 4 pis. 

B 284. Report on progress of investigations of the mineral resources of Alaska in 1905, by A. H. Brooks and others. 1906. 
169 pp., 14 pis. 

B 285. Contributions to economic geology, 1905; S. F. Emmons and E. C. Eckel, geologists in charge. 1906. 506 pp., 13 pis. 
B 286. Economic geology of the Beaver quadrangle, Pennsylvania, by L. II. Woolsey. 1906. 132 pp., 3 pis. 

B 287. Juneau gold belt, Alaska, by A. C. Spencer, and A reconnaissance of Admiralty Island, Alaska, by C. W. Wright. 
1906. 161 pp., 27 pis. 

PP 54. The geology and gold deposits of the Cripple Creek district, Colorado, by W. Lindgren and F. L. Ransome. 1906. 
516 pp., 29 pis. 

SERIES B, DESCRIPTIVE GEOLOGY. 

B 23. Observations on the junction between the Eastern sandstone and the Keweenaw series on Keweenaw Point, Lake 
Superior, by R. D. Irving and T. C. Chamberlin. 1885. 124 pp., 17 pis. (Out of stock.) 

B 33. Notes on geology of northern California, by J. S. Diller. 1886. 23 pp. (Out of stock.) 

B 39. The upper beaches and deltas of Glacial Lake Agassiz, by Warren Upham. 1887. 84 pp., 1 pi. (Out of stock.) 

B 40. Changes in river courses in Washington Territory due to glaciation, by Bailey Willis. 1887. 10 pp., 4 pis. (Out of 
stock.) 

B 45. The present condition of knowledge of the geology of Texas, by R. T. Hill. 1887. 94 pp. (Out of stock.) 

B 53. The geology of Nantucket, by N. S. Shaler. 1889. 55 pp., 10 pis. (Out of stock.) 

B 57. A geological reconnaissance in southwestern Kansas, by Robert Hay. 1890. 49 pp., 2 pis. 

B 58. The glacial boundary in western Pennsylvania, Ohio, Kentucky, Indiana, and Illinois, by G. F. Wright, with intro¬ 
duction by T. C. Chamberlin. 1890. 112 pp., 8 pis. (Out of stock.) 

B 67. The relations of the traps of the Newark system in the New Jersey region, by N. H. Darton. 1890. 82 pp. (Out of 
stock.) 

B 104. Glaciation of the Yellowstone Valley north of the Park, by W. H. Weed. 1893. 41 pp., 4 pis. 

B 108. A geological reconnaissance in central Washington, by I. C. Russell. 1893. 108 pp., 12 pis. (Out of stock.) 

B 119. A geological reconnaissance in northwest Wyoming, by G. H. Eldridge. 1894. 72 pp., 4 pis. 

B 137. The geology of the Fort Riley Military Reservation and vicinity, Kansas, by Robert Hay. 1896. 35 pp., 8 pis. 

B 144. The moraines of the Missouri Coteau and their attendant deposits, by J. E. Todd. 1896. 71 pp., 21 pis. 

B 158. The moraines of southeastern South Dakota and their attendant deposits, by J. E. Todd. 1899. 171 pp., 27 pis. 

B 159. The geology of eastern Berkshire County, Massachusetts, by B. K. Emerson. 1899. 139 pp., 9 pis. 

B 165. Contributions to the geology of Maine, by H. S. W’illiams and H. E. Gregory. 1900. 212 pp., 14 pis. 

WS 70. Geology and water resources of the Patrick and Goshen Hole quadrangles in eastern Wyoming and western 
Nebraska, by G. I. Adams. 1902. 50 pp., 11 pis. 

B 199. Geology and water resources of the Snake River Plains of Idaho, by I. C. Russell. 1902. 192 pp., 25 pis. 

PP 1. Preliminary report on the Ketchikan mining district, Alaska, with an introductory sketch of the geology of south¬ 
eastern Alaska, by A. H. Brooks. 1902. 120 pp., 2 pis. 

PP 2. Reconnaissance of the northwestern portion of Seward Peninsula, Alaska, by A. J. Collier. 1902. 70 pp., 11 pis. 

PP 3. Geology and petrography of Crater Lake National Park, by J. S. Diller and H. B. Patton. 1902. 167 pp., 19 pis. 

PP 10. Reconnaissance from Fort Hamlin to Kotzebue Sound, Alaska, by way of Dali, Kanuti, Allen, and Kowak rivers, 
by W. C. Mendenhall. 1902. 68 pp., 10 pis. 

PP 11. Clays of the United States east of the Mississippi River, by Heinrich Ries. 1903. 298 pp., 9 pis. 

PP 12. Geology of the Globe copper district, Arizona, by F. L. Ransome. 1903. 168 pp., 27 pis. 

PP 13. Drainage modifications in southeastern Ohio and adjacent parts of West Virginia and Kentucky, by W. G. Tight. 
1903. Ill pp., 17 pis. (Out of stock.) 

B 208. Descriptive geology of Nevada south of the fortieth parallel and adjacent portions of California, by J. E. Spurr. 
1903. 229 pp.,8 pis. 

B 209. Geology of Ascutney Mountain, Vermont, by R. A. Daly. 1903. 122 pp., 7 pis. 

WS 78. Preliminary report on artesian basins in southwestern Idaho and southeastern Oregon, by I. C. Russell. 1903. 
51 pp., 2 pis. 

PP 15. Mineral resources of the Mount Wrangell district, Alaska, by W. C. Mendenhall and F. C. Schrader. 1903. 71 pp., 
10 pis. 

PP 17. Preliminary report on the geology and water resources of Nebraska west of the one hundred and third meridian, 
by N. H. Darton. 1903. 69 pp., 43 pis. 

B 217. Notes on the geology of southwestern Idaho and southeastern Oregon, by I. C. Russell. 1903. 83 pp., 18 pis. 

B 219. The ore deposits of Tonopah, Nevada (preliminary report), by J. E. Spurr. 1903. 31 pp., 1 pi. 


IV 


SERIES LIST. 


PP 20. A reconnaissance in northern Alaska in 1901, by P. C. Schrader. 1904. 139 pp., 16 pis. 

pp 21. The geology and ore deposits of the Bisbee quadrangle, Arizona, by F. L. Ransome. 1904. 168 pp., 29 pis. 

WS 90. Geology and water resources of part of the lower James River Valley, South Dakota, by J. E. Todd and C. M. Hall. 
1904. 47 pp., 23 pis. 

PP 25. The copper deposits of the Encampment district, Wyoming, by A. C. Spencer. 1904. 107 pp., 2 pis. 

PP 26. Economic resources of the northern Black Hills, by J. D. Irving, with contributions by S. F. Emmons and T. A. 
Jaggar, jr. 1904. 222 pp., 20 pis. 

PP 27. A geological reconnaissance across the Bitterroot Range and Clearwater Mountains in Montana and Idaho, by 
Waldemar Lindgren. 1904. 122 pp., 15 pis. 

PP 31. Preliminary report on the geology of the Arbuckle and Wichita mountains in Indian Territory and Oklahoma, 
by J. A. Taft', with an appendix on reported ore deposits in the Wichita Mountains, by H. F. Bain. 1904. 97 pp., 
8 pis. 

B 235. A geological reconnaissance across the Cascade Range near the forty-ninth parallel, by G. O. Smith and F. C. 
Calkins. 1904. 103 pp.,4 pis. 

B 236. The Porcupine placer district, Alaska, by C. W. Wright. 1904. 35 pp., 10 pis. 

B 237. Igneous rocks of the Highwood Mountains, Montana, by L. V. Pirsson. 1904. 208 pp., 7 pis. 

B 238. Economic geology of the Iola quadrangle, Kansas, by G. I. Adams, Erasmus Haworth, and W. R. Crane. 1904. 
83 pp., 1 pi. 

PP 32. Geology and underground water resources of the central Great Plains, by N. H. Darton. 1905. 433 pp., 72 pis. 

WS 110. Contributions to hydrology of eastern United States, 1904; M. L. Fuller, geologist in charge. 1905. 211 pp., 5 pis. 
B 242. Geology of the Hudson Valley between the Hoosic and the Kinderhook, by T. Nelson Dale. 1904. 63 pp.,3 pis. 
PP 34. The Delavan lobe of the Lake Michigan Glacier of the Wisconsin stage of glaciation and associated phenomena, by 
W. C. Alden. 1904. 106 pp., 15 pis. 

PP 35. Geology of the Perry Basin in southeastern Maine, by G. G. Smith and David White. 1905. 107 pp., 6 pis. 

B 243. Cement materials and industry of the United States, by E. C. Eckel. 1905. 395 pp., 15 pis. 

B 246. Zinc and lead deposits of northeastern Illinois, by H. F. Bain. 1904. 56 pp., 5 pis. 

B 247. The Fairhaven gold placers of Seward Peninsula, Alaska, by F. H. Moftit. 1905. 85 pp., 14 pis. 

B 249. Limestones of southwestern Pennsylvania, by F. G. Clapp. 1905. 52 pp., 7 pis. 

B 250. The petroleum fields of the Pacific coast of Alaska, with an account of the Bering River coal deposit, by G. C. 
Martin. 1905. 65 pp., 7 pis. 

B251. The gold placers of the Fortymile, Birch Creek, and Fairbanks regions, Alaska, by L. M. Prindle. 1905. 16 pp., 
16 pis. 

WS 118. Geology and water resources of a portion of east-central Washington, by F. C. Calkins. 1905. 96 pp., 4 pis. 

B 252. Preliminary report on the geology and water resources of central Oregon, by I. C. Russell. 1905. 138 pp., 24 pis. 

PP 36. The lead, zinc, and fluorspar deposits of western Kentucky, by E. O. Ulrich and W. S. Tangier Smith. 1905. 
218 pp., 15 pis. 

PP 38. Economic geology of the Bingham mining district of Utah, by J. M. Boutwell, with a chapter on areal geology, by 
Arthur Keith, and an introduction on general geology, by S. F. Emmons. 1905. 413 pp., 49 pis. 

PP 41. The geology of the central Copper River region, Alaska, by W. C. Mendenhall. 1905. 133 pp., 20 pis. 

B 254. Report of progress in the geological resurvey of the Cripple Creek district, Colorado, by Waldemar Lindgren and 
F. L. Ransome. 1904. 36 pp. 

B 255. The fluorspar deposits of southern Illinois, by H. Foster Bain. 1905. 75 pp., 6 pis. 

B 256. Mineral resources of the Elders Ridge quadrangle, Pennsylvania, by R. W. Stone. 1905. 85 pp., 12 pis. 

B 257. Geology and paleontology of the Judith River beds, by T. W. Stanton and J. B. Hatcher, with a chapter on the 
fossil plants, by F. H. Knowlton. 1905. 174 pp., 19 pis. 

PP 42. Geology of the Tonopah mining district, Nevada, by J. E. Spurr. 1905. 295 pp., 24 pis. 

WS 123. Geology and underground water conditions of the Jornada del Muerto, New Mexico, by C. R. Keyes. 1905. 
42 pp., 9 pis. 

WS 136. Underground waters of Salt River Valley, Arizona, by W. T. Lee. 1905. 194 pp., 24 pis. 

PP 43. The copper deposits of Clifton-Morenci, Arizona, by Waldemar Lindgren. 1905. 375 pp., 25 pis. 

B 265. Geology of the Boulder district, Colorado, by N. M. Fehneman. 1905. 101 pp., 5 pis. 

B 267. The copper deposits of Missouri, by H. F. Bain and E. O. Ulrich. 1905. 52 pp., 1 pi. 

PP 44. Underground water resources of Long Island, New York, by A. C. Veatch and others. 1905. 394 pp., 34 pis. 

WS 148. Geology and water resources of Oklahoma, by C. N. Gould. 1905. 178 pp., 22 pis. 

B 270. The configuration of the rock floor of Greater New York, by W. H. Hobbs. 1905. 96 pp., 5 pis. 

B 272. Taconic physiography, by T. M. Dale. 1905. 52 pp., 14 pis. 

PP 45. The geography and geology of Alaska, a summary of existing knowledge, by A. H. Brooks, with a section on climate, 
by Cleveland Abbe, jr.. and a topographic map and description thereof,by R.M. Goode. 1905. 327 pp., 34 pis. 

B 273. The drumlins of southeastern Wisconsin (preliminary paper), by W. C. Alden. 1905. 46 pp., 9 pis. 

PP 46. Geology and underground water resources of northern Louisiana and southern Arkansas, by A. C. Veatch. 1906. 
422 pp., 51 pis. 

PP 49. Geology and mineral resources of part of the Cumberland Gap coal field, Kentucky, by G. H. Ashley and L. C. Glenn, 
in cooperation with the State Geological Department of Kentucky, C. J. Norwood, curator. 1906. 239 pp., 40 pis. 
PP 50. The Montana lobe of the Keewatin ice sheet, by F. H. H. Calhoun. 1906. 62 pp., 7 pis. 

B 277. Mineral resources of Kenai Peninsula, Alaska: Gold fields of the Turnagain Arm region, by F. H. Moffit, and the 
coal fields of Kachemak Bay region, by R. W. Stone. 1906. 80 pp., 18 pis. (Out of stock.) 

WS 154. The geology and water resources of the eastern portion of the Panhandle of Texas, by C. N. Gould. 1906. 
64 pp., 15 pis. 


SERIES LIST. 


V 


B 278. Geology and coal resources of the Cape Lisburne region, Alaska, by A. J. Collier. 1906. 54 pp., 9 pis. 

B 279. Mineral resources of the Kittanning and Rural Valley quadrangles, Pennsylvania, by Charles Butts. 1906. 198 pp., 
11 pis. 

B 280. The Rampart gold placer region, Alaska, by L. M. Prindle and F. L. Hess. 1906. 54 pp., 7 pis. 

B 282. Oil fields of the Texas-Louisiana Gulf coastal plain, by N. M. Fenneman. 1906. 146 pp., 11 pis. 

WS 157. Underground water in the valleys of Utah Lake and Jordan River, Utah, by G. B. Richardson. 1906. 81 pp., 9 pis. 

PP 51. Geology of the Bighorn Mountains, by N. II. Darton. 1906. 129 pp., 47 pis. 

WS 158. Preliminary report on the geology and underground waters of the Roswell artesian area, New Mexico, by 
C. A. Fisher. 1906. 29 pp., 9 pis. 

PP 52. Geology and underground waters of the Arkansas Valley in eastern Colorado, byN. II. Darton. 1906. 90 pp., 28 pis. 
WS 159. Summary of underground-water resources of Mississippi, by A. F. Crider and L. C. Johnson. 1906. 86 pp., 6 pis. 

PP 53. Geology and water resources of the Bighorn basin, Wyoming, by C. A. Fisher. 1906. 72 pp., 16 pis. 

B 283. Geology and mineral resources of Mississippi, by A. F. Crider. 1906. 99 pp., 4 pis. 

B 286. Economic geology of the Beaver quadrangle, Pennsylvania (southern Beaver and northwestern Allegheny coun¬ 
ties), by L. H. Woolsey. 1906. 132 pp., 8 pis. 

B 287. The Juneau gold belt, Alaska, by A. C. Spencer, and a reconnaissance of Admiralty Island, Alaska, by C. W. Wright. 
1906. 161 pp., 37 pis. 

PP 54. The geology and gold deposits of the Cripple Creek district, Colorado, by Waldemar Lindgren and F. L. Ransome. 
1906. 516 pp., 29 pis. 

Correspondence should be addrest to 

The Director, 

United States Geological Survey, 

Washington, D. C. 


November, 1906. 




U S.GEOLOGICAL SURVEY 


PROFESSIONAL PAPER NO. 54 PL. I 




w\ 


Ulet.t 


'IOSJW- 


-JOtjn, 


r ^ 

10089 


arbonate H 


b*ot Hill** 


A $>94/. 


C'Rf) kkj;j 


.JOOOo. 




Itil/VICYW 


’i cLwiO 


Lookout Point 




'oooo‘ 


Grouse' Hill 


Straub" 


Bri nd 


I Kit.clrtovrn, 


ileason 
P/ild Horse 


TOPOGRAPHIC MAP OF THE CRIPPLE CREEK DISTRICT, COLORADO 

Scale 25000 


2 miles 


2 kilometers 


MINE NAMES 


AND NUMBERS 


Henry Gannett,Chief Topographer 

Topography by W. B.Corse.T. M. Ban non, and E.M. Douglas 

Triamgulation by E.M.Douglas 

Surveyed in 1894 

Revisedin 1902 1903 by R.T.Evans 
E.M.Douglas, Geographer in charge 


1 Metallic tunnel 

2 Galena tunnel 

3 York tunnel 

4 Grand Review 

5 Nickel Plate 

6 Ida May 

7 Fluorine 

8 Standard 


173 Gold Dollar 

174 Prince Albert 

175 Beacon 

176 Black Bell 

177 Jack G. 

178 Gregory 

179 Snowy Range 

180 Wide Awake 


9 Greutschamacher 181 Cranks 


tunnel 
10 May Bell 
1! Wazee 

12 Lincoln 

13 Hawkeye 

14 Bolivar 

15 Cuckoo 

16 Aztec 

17 Bondholder 

18 Laura Lee 

19 Addle C. 

20 Sunflower 

21 Roanoke 

22 Tenderfoot Consol 194 Ida May 

23 Bonanza King No. 2 195 Joe Dandy 

24 Black Diamond 

25 Queen Bess 

26 Mollie Kathleen 

27 Gold King 

28 Reno 

29 C. O. D. 

30 May-be-so 

31 Bob Lee 

32 Friday 

33 Hoosier 

34 Detroit 

35 Newark 

36 Jeanette 

37 Pride of C. C. No. 2 207 Mar y Ann 

208 Sadie Bell 


182 Custer 

183 Lizzie S. 

184 Bonnie Nell 

185 Moose 

186 Cresson 

187 Trail tunnel 

188 Comanche Plume 

tunnel 

189 Uinta tunnel 

190 Orphia tunnel 

191 Eclipse 

192 Carbonate Queen 

193 Brigadier 


196 Red Umbrella 

197 Rattler 

198 Maggie 

199 Jackson Shaft 

200 Gold Sovereign 

tunnel 

201 Draper 

202 Ben Harrison 

tunnel 

203 Mary L. 

204 Bertha B. 

205 Little Frank 

206 Elsie R. 


38 Junebug 

39 Leon 

40 Sunshine 

41 Dorothy 

42 Queen Ann 

43 Mariposa 

44 Quito 

45 Goodwill tunnel 

46 Alpha tunnel 

47 Red Spruce 

48 Pointer 

49 Ophelia tunnel 

50 World’s Fair 

51 Chicago tunnel 

52 Abe Lincoln 

53 Uly 

54 Gold Pass 

55 Globe 

56 Moon Anchor 

57 Midget 

58 City View 

59 Progress-Gold King 

60 Half Moon 


209 Blue Bird 

210 Lucky Guss No. 1 

211 Lafayette 

212 Ruble 

213 Mountain Beauty 

214 Lucky Guss No. 2 

215 Orpha May 

216 Findley 

217 Atlantic 

218 Deadwood No. 2 

219 Pearl 

220 Trachyte 

221 Shurtloff No. 2 

222 Deadwood No. I 

223 Venture 

224 Victor 

225 Smuggler 

226 Little Daisy 

227 Little May 

228 Baby Mine 

229 Easter Bell 

230 Bull Hill Sampler 


61 Anchon.-Lel.ntl 231 T - and 8 - Simpler 


232 Vindicator No. 2 

233 Vindicator No. 1 

234 Lillie 


62 Volcano 

63 Lexington 

64 International 

65 E. Porter Colt) King 235 Lo " ef ' ll ' >w 

66 KittenhouM 236 Chris,mas 

67 Cr.ce Greenwood ^ La 8eda 

68 Union Bell 238 Usl Dollar 

69 Mint 

70 Alamo 

71 Superior 

72 Fauntleroy 

73 Virginia M. 

74 Howard 

75 Work No. 4 

76 Dolly Varden 

77 Mountain Monarch 247 Little Caddy 

78 North Star 248 Bessie 

79 Plymouth Rock No. 2 249 Safety 

80 Deorhorn 250 Gold Knob 

81 Ironclad 251 Star 

82 Plymouth Rock No. 1 252 Rigi No. 1 

83 South Park 253 Rigi No. 2 

84 New York tunnel 254 Modoc No. 1 

85 Josephine tunnel 255 Portland No. 3 

86 Anna May Wells 256 Eagle Sampler 


239 Los Angeles 

240 Colorado City 

241 Modoc No. 2 

242 Florence 

243 Clyde 

244 Golden Cycle 

245 Theresa 

246 Homes take 


87 Manda 

88 Bogart 

89 Sheriff 

90 Maria A. 

91 Twin Sisters 

92 Anaconda 

93 Nabob 

94 Arapahoe 

**' Jerry Johnson 


Eagle 

New Century 
Elsmere 
Flying Cloud 
Mitchell 
Pinnacle 
Blanch 
i 10e Acacia 

109 Comet 

110 Buena Vista 

111 Lee 

I 112 Block 10 

113 Block 9 

114 Block 8 

115 Block 7 

116 Morning Star 
1 417 Gold Bond 

118 Peg Leg 


257 National Sampler 

258 Van Fleet Sampler 

259 Portland No. 2 

260 Lowell 

261 Granite 

2£2 Portland No. I 

263 T. and B. Sampler 

264 Chesapeake 

265 Stratton’s 
Independence No.2 

266 Monument 

267 Stonehouse 

268 Dillon 

269 Par Value 

270 Stratton's 
Independence No. 1 

271 Strong 

272 Mary Cashen 

273 Dead Pine 

274 Oliver 

275 Ajax 

276 Coriolanus 

277 Nellie V. 

278 Mohican 

279 Green 

280 May B. 

281 Alhambra 

282 Santa Rita 

283 Nevada King 

284 Climax 

285 Grace 

286 Forepaugh 


119 Sweet, or El Rlno 287 Golcood. 

120 C»ledonle 288 d»M Coin 


289 Jolly Tar 

290 Jefferson 

291 Conio 

292 Fortune 

293 Jolly Jane 

294 Mattie W. 

295 Surety 

296 Trinidad 
Gold Queen 

297 St. Patrick 

298 Bonzai 

299 King Solomon’s 
Placer 

300 Alliance 

301 Hawkeye 

302 Teal tunnel 

303 Likely 

304 Marigold 

305 Cowboy 

306 Old Gold and 
Globe mill 

307 Hildebrand 

308 Newell tunnel 

309 El Paso drainage 
tunnel 

310 Arequa mill 

187 Elizabeth Cooper 3 '> J°»" A. U*« 
its lennie S.mdT 312 A”*™*" 


121 Cardinal 

122 Cumberland 
I 123 Dead Shot 

124 Mary Nevln 

125 National tunnel 

126 C. K. St N. 

127 El Paso 

128 Rocky Mt. 

I 129 Standard tunnel 
I 130 Banner 
1131 Shannon 
I 132 Arno 

1133 Work No. 10 

1134 Work No. 1 

1135 Work No. 11 

1136 Mary McKinney 
] 137 Advance No. 2 

1138 Morning Glory 

1139 Jackpot 

1140 Doctor 

1141 Ingham 

1142 Work No. 5 

1143 Nugget 

1144 Work No. 6 

1145 Advance 

1146 Golden Wedge 


|148 Jennie Sample 

1149 Katin ka 

1150 Wedge 

■ 151 Ophir 

1152 Tornado 

1153 Upper Raven 
tunnel 

1154 Lower Raven 
tunnel 

1155 Bostwick 

1156 Elkton 

1157 Thompson 

1158 Kitty Lane 

1159 Ross and Hurd 
tunnel 

1160 Economic Mill 

1161 Squaw Mr. 

1162 3 H. 

1163 Alice 

1164 Dan McDonald 

1165 Little Bess 
1*66 Maid of Orleans 
1167 Agnes 

■ 168 St. Thomas 
■169 Savage 
Il70 Mabel M. 

|I71 Little Nell 
|l 72 Zoe 


313 Hannah Britt 

314 Conundrum 

315 Empire State 

316 Pinto 

317 Burns 

318 Pharmacist 

319 Zenobia 

320 Little May 

321 Hull City placer 

322 Anaconda-Raven 

tunnel 

323 Kentucky Belle 

324 Old Gold 

325 W. P. H. 

326 Little Pedro 

327 Forest Queen 

328 Pride of Cripple 

Creek 

329 Vogelman 

330 Dexter 

331 Ramona 

332 Henry Adney 

333 Trilby 

334 Le Claire 

335 Dante 

336 Whisper 

337 Blue Bell 

tunnel 


105° 12'2 E 


R. 69 W. 


6 I05°05'45' 

38 


R 70 W 


38T-* % 


I05°I2'2I* 


R .70 W 


$ '-Re"! 


LEGEND 


H 


Shaft 


X 


Prospect 


Y 

Mine tunnel 


V wf 

Mine dump 


A 


Triangulation 

station 


B.M. 


Bench mark 



Roads and 
buildings 


Contour interval 50feet 

.Datum, is mean sea level 











































































































































































































































































I05°0545* 


• pi v 




•llleljl ^ 




jGarbonate Hilt . 


roty-w 


%s\4g 


Mr.Pisgab 


GaPVa H 




■/VSOO 


Calf Mt 




S^m.uii-V 


ggu&STNA ' “ ' 

.lroncJadjmA 


jgfig 




/iot6r- Pass 

pf/'W* 

K “ ■ - 


oldlh'pd 


Sj,q M a> M|t 


WmM 

g? -1 *duL4h 


lismt 

’Dsdi; 


v.v.7-/j 


)) M ,L*iwi-t r rjc*^ 




Bri nd Mtf 




105 !2’2I 


Henry Gan nett,Chief Topographer 

Topography by W. B.Corse,T. M.Bannon.and E.M. Douglas 
Triangulation by E.M.Douglas 
Surveyed in 1894 

Revised in 1902-1903 by R.T.Evans 
E.M.Douglas, Geographer in charge 


GEOLOGIC MAP AND SECTIONS OF THE CRIPPLE CREEK DISTRICT, COLORADO 

_ , l_ 

, Scale 2500o 


Geology by F. L.Ransome and L.C.Graton 
Surveyed in 1903 


2 miles 


»kilometers 


Contour interval 50feet 
.Datum is mean sea level 


JULIUS BIEN 8.C0.LITH N V 


U.S.GEOLOGICAL SURVEY 


PROFESSIONAL PAPER NO. 54 PL 


LEGEND 


SEDIMENTARY ROCKS 


Alluvium 

Clays,sands, and gravels 
of'valleys 


Landslides 


m 


Moraines 

Composed chiefly of' 
granitic materials 


Sands,gri ls,ai id conglomera tes. 

derived chiefly from granitic-rocks 


IGNEOUS ROCKS 


Basic dikes 

(bmpris ing Ira chydoleixtc 
vogesHe. andntonchiquits 






: • 


rrachydoleriu 


Intrusive mass of Bull Clift 


Phonolite 

In trusive masses and dikes- 


m 

L atite - pi i on o ljte 

Intrusive masses and dikes 
with transitions to syenite 


Syenite 

Intrusive masses with transitions 
to latite-phonolite 


Breccia 

Breccias with tuffs and agglomerates, 
composed chiefly of phonolite and 
latite-phonolife, locally containing 
abundant fragments of granite,gneiss, 
or schist /tufts occasionally bedded 


_ 


hie 


Kil 


Intrusive sheets 


Diabase 

Dikes and smalt irregular masses 


Olivine syenite 
Intrusive mass consisting of 
o livinc s ven ite, two f a vies 
ofolivine gabbro, and dike of anorthosite 


Spring Creek granite 


Cripple Creek granite 


Pikes Peak granite 


METAM0RPHIC ROCKS 


Gneiss 

Quartz feldspar bio die gneiss 
probably derived from granite 


Mimm 

Schist 

Quartz - muscovite ■ f'ibrof its schist . 
possibly derived from sediments 


Shafts 

x 

Prospects 


Mine tunnels 




























































































































































































































































PROFESSIONAL PAPER N 


Hoosiei 


.unshine incline 


Plymouth Rock 


Pride of C C 


leerhorn 


9611 | 

ibe Lincoln 


Jackson sh 


Porter 


JerryJohnson 
incline 

Da.non incline 


Da mon ma m £ 


Geneva' 


'NPinnacle 
'hipp& Glenn 


'Johnson 
\Hilf Moon 


Moon Anchoi 


Conundrum 


Londonderry 


Puritan 


Climax 


lona 


Parker 

10216 


Ellithorp 


Grube 


yv *exirigto 


Comet 


jeff Davis 


Mariposa 


Murphv 


Jaycox 


BuenaVista 


Parker 


re. Porter 
Gold King 


fild Horse 

10652 


.Hillside 


uWrocklofP 


Maloney™ 


Parker 4 Gardim 


Grotto 


£ Lee incline 
.Lee io«io 


White 


Burns 


Rob'Roy 


Smugglei 


Pharmacist incline 


.Ramona 


Happy Yea 


Great View 
10006 


Zenobiarcraii 


iZenobia incline 


leys tone 


Keiths 


Deadw ood No.i 


Accident, 

9566 


’ictor incline 


Do'lly Varden 


Pointer 


Favorite 


Trachyte No. 


STANTARD TUNNEL 


Portal 9268 


i rouse 


lead wood No 2 


’ikes Peak inciini 


Russell 4 Sharpe 


»/ / Porcupine 


Deadwooa No3 


.Seamon 


lonning Glory 
incline / 


loberts 


Birch 

9610 


■Lucky Guss No.2 


Ingham incline 


10538' 


awkins 


Greeta incline 


Rawson 


'New Haven 


9050 


Jacksoi 


Mackin 


Wiches 


Jackpot 

incline/ 


.Gregory i 028 ? 


Bertha 

10223 


9048 


.leoonia 


Jennie Sampu 
10036 / 


Sexton \ 


Constantine 


Mary! 
f 10022 


iRaven 
incline 


Tornado 

10124 


Moose'* 


Alsa R. ioo 65 


« Rati nka 

9800 


Six Points 


•istmas 


ChrNo.3 


.astDolli 

I027S 


Bonnie Nell 
£; 10047 


Dex1er3; 


Moose disc 
10026 


,owe» 


ate man 


lorence 


Juminum 


Hawke' 


I odoc incline 


Modoc 


Portland No3 


,yen\te and latite- 
eiss.and schist 

Thompsor 


Carb.Queen 


9627 


/Whiling 9464 
label M 9493 


Portland No 2 

10244 


Coriolanus 


Goid Dollar 9488 


Monumeht 


mouse 


B. incline 

9852 


South shaft 


ParValui 


Independence 

9843 


,ry Cashen 

W 9764 


Gold Coin 
incline 


ItINCII>AL UNI)ER GROUND WORKINGS 
CRIPPLE CREEK. COLORADO i 


Golconda 


HomeRun 

9591 


BvWaldemar Lindgron and KL.Ransome.Drawn by J.L.Bruet 


JUL 'JS P EM C 0 lIFp N V 


















































































































































































































































































































Ill Id '-bS'ON a3dVcMVNOISS3JOad 


















































































« 

























































' 













- 










' 

3 















































































































































































































































































































































































































